Still Have Concerns

The eye spot may (I say may) be the start of a cataract which can lead to blindness; I've had fish with this, in fact one of my Diamond Tetra has this in the left eye now.  It is not treatable, and likely due to genetics or perhaps injury.  On the other hand, this may turn into nothing.
 
I don't want to start suggesting things for the white bump.  I would just observe the fish.  I've seen this too.
 
B.

Just been doing some searching, and it could just be the pupil I'm seeing, or maybe not. I don't notice it on the other Minnows, at least I haven't yet, but looked at from different angles, the eyes go from black to a gold/red colour. Probably just the light reflecting off the eye, as the Minnows don't seem to have trouble finding their way around the tank at all (so not blindness, although the male Minnow in the video I posted - the one with the spot above his right eye - did awkwardly brush past some Vallisneria this evening).

Took a TDS reading this evening, it was coming in at 253-255ppm. Last time I tested - 4 weeks ago - it was around 232-234ppm. Quite a jump within a month. I'll have to keep an eye on that, as part of the issue might be my tap water (which I haven't tested). I do try to get as close as I can to 0.25ml Prime per 10 litres added, although I go slightly above to err on the side of caution.
 
EDIT: Just tested my tap water. Filled a glass after swilling it out - didn't wipe it or anything, just filled it a few times and emptied it out (maybe I should have wiped it more thoroughly, so possible contamination?) - and got readings of 259ppm and above into the 260s. That's today, but it's fair to assume it might be contributing to the higher TDS in my tank.
 
EDIT 2: Ran the water for a bit longer and swilled the glass out some more (after leaving the previous test water standing for 30-40 minutes). Additional tests put it at 259ppm and above into the 260s, as before. Cold water being tested, not warm/hot water. I don't push the tap all the way to hot when filling buckets with water for water changes, so am I right in assuming I'd have a mix of cold water from outside our house and hot water from our water tank?

With the fish species you have, the TDS at these numbers is not a problem.
 
To the hot/cold question, yes.

As to the white spot/bump on the male Minnow, it was still there throughout today. I don't think it looks fuzzy, and hopefully that isn't to come... I haven't yet observed his poo. The Minnows don't seem to poo all that much these days... The one female Minnow did seem to have white, rather chunky poo the other day (think it was yesterday, Sunday 3rd May - or it was the day before, Saturday 2nd May, one of the two), might have been slimy and might not have been. It broke off in a small chunk. No long trail of poo, though.

I was thinking of filling a 1 litre water jug with a mix of hot/cold similar to what I use during a water change so I could test the TDS, but it might not be an accurate parallel. I don't think a drop from the pipettes I use is equivalent to 0.025ml, so I might end up over-dosing on the Prime into the test sample (not very useful).
 
Also, am I correct in assuming the warm water is really just cold water from outside of the house put through an additional process over the course of a number of hours, with there being very little reason for it to be drastically different in TDS levels compared to the cold water (excepting the presence of heavy metals from the hot water tank)? I also note that I didn't dechlorinate the test sample last night, so I am not sure if chlorine and chloramine would affect the TDS results.
 
The best time for me to test TDS of the tap water is right before adding it to the tank during a water change; then I'm measuring a real situation and not hypothetical situations, and dosing with the (just about) appropriate amount of Prime (a drop extra or two wouldn't distort the results as much as in a small scale test on a litre or a few litres).

Kaidonni said:

I was thinking of filling a 1 litre water jug with a mix of hot/cold similar to what I use during a water change so I could test the TDS, but it might not be an accurate parallel. I don't think a drop from the pipettes I use is equivalent to 0.025ml, so I might end up over-dosing on the Prime into the test sample (not very useful).
 
Also, am I correct in assuming the warm water is really just cold water from outside of the house put through an additional process over the course of a number of hours, with there being very little reason for it to be drastically different in TDS levels compared to the cold water (excepting the presence of heavy metals from the hot water tank)? I also note that I didn't dechlorinate the test sample last night, so I am not sure if chlorine and chloramine would affect the TDS results.
 
The best time for me to test TDS of the tap water is right before adding it to the tank during a water change; then I'm measuring a real situation and not hypothetical situations, and dosing with the (just about) appropriate amount of Prime (a drop extra or two wouldn't distort the results as much as in a small scale test on a litre or a few litres).

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I really wouldn't fuss over TDS here.  I mean, what can you do about them anyway, even if they were an issue for these fish which they're not.
 
I would assume your house has a hot water heating tank.  There is a line from the municipal water to this tank, and the tank heats the water.  Mineral deposits from the tank itself have been known, but most of us do not worry about this either.

A little update - it doesn't look like there's been any change to the spot since Sunday.

Some pics I took today of the white spot/bump.

On the Practical Fishkeeping forum, it's been suggested the Minnow has mouthrot, and that the 'front part' (his mouth?) isn't good as well. I'm not sure if I notice anything untoward on his actual mouth as far as the two white areas are concerned; these are that small that it could be normal colouration, or a small fungus developing, it's that hard to tell. I'm not sure any photos or video would help because it's going smaller than the white spot/bump above the eye. I do think the white marks on his mouth seem almost symmetrical in positioning, although not entirely, so it could be normal colouration...but I mention this because I don't want to assume and end up wrong.
 
It's also been suggested the white spot/bump above the eye might be a tumour.

I would agree with both suggestions, but again I repeat that I am not by any means an expert in disease issues.  But if those who are knowledgeable have suggested what you report, I would tend to agree.

I've researched columnaris, but I'm hesitant to chalk it up to that. Possibly bacterial, but again, once I dose with any medicine, there's no going back.

Two more pics...

His mouth does look rather red in real life, but then images online of White Cloud Mountain Minnows show them having red areas around their mouth.

Kaidonni said:

I've researched columnaris, but I'm hesitant to chalk it up to that. Possibly bacterial, but again, once I dose with any medicine, there's no going back.

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This is not columnaris, which I have once had.