Tiny white/grey dots and patches [livebearers]

[emeraldking]

Hi, looks like it's got a couple of growths on both sides. If it's something tumorous, then it's no wonder why other fish are okay. if it is a something tumorous, then it's not weird if he's doing the shimmy. But even ich can look like this is a progressed way. Because you've been mentioning that others sometimes scratch and have pinprick-sized dots here and there. And this specimen could just be weaker that it loks a bit more worse than those other fish.

Your female will probably still be there. For this species can hide a lot. Same thing overhere... Mostly the young ones are more in sight than the adults.

 

[Abaddon]

Well, I just noticed that one of the other males in the display tank has developed a weird slightly protruding bump on top of his back. I managed to get some more photos. It seems to have appeared out of nowhere & looks like a tiny grain of rice atttached to his skin (similar to what the female had on her tail). Again, he has no other symptoms and is chasing the females around trying to breed lol. I honestly don't know what it is... the spots & patches seem to pop up very suddenly & then disappear without any other obvious symptoms (other than scratching). I just did a WC yesterday & now all of a sudden this spot has popped up & I saw my biggest female trying to scratch herself & having a bit of a frantic/jumpy swimming pattern (no skin changes though). All the other fish are calmly cruising around the tank & she's glass surfing in one corner - she's been doing this on and off since I got her, though.
The quarantined male perked up and stopped shimmying after I removed the meds and did a big water change (and added a few floating plants to make him more comfortable). Which is a bit counterintuitive... He's now marinating in some salt , we'll se if that helps.
I'm now torn between some kind of (protozoan?) parasite, tetrahymena (since it's a livebearer) or epistylis (I hope not)... but I've heard conflicting things about it. Some people say it's deadly and progresses quickly, others say it isn't. So I'm not entirely sure what to do. The fish aren't showing any signs of a bacterial infection as far as I can tell. But if it is epi or tetrahymena, is the treatment basically the same as for ich (methylene blue & malachite green) - assuming the are no additional infections on top of it?
Note: this is a new tank (~2 months old), but last I checked the parameters were all fine... unless there is some kind of bacterial pathogen in the water, but then how do I get rid of it without nuking the biofilter and every living thing in the tank? Would a few big water changes be enough? Or maybe a UV sterilizer (the kind you mount on the internal filter outlet) - would that also potentially eliminate any free-swimming parasites?

 

[Abaddon]

@emeraldking I gave the male a pretty high concentration salt bath (almost ~2tsp per 2l) and the spots/bumps on his skin seem to have gotten worse for some reason. There's now more than before, and they seem to be more prominent. I also noticed a few long strands that looked like tiny hairs or very thin worms starting to come out from the bumps following the salt bath (there was a really long one attached to his tail, but it fell off pretty quickly & I'm not sure if it wasn't just a strand of hair algae, since there's a lot of it in the tank with him. But it looked disgusting ) Plus he has a bunch of tiny white streaks on his dorsal fin and tail (pictured). I've taken a few pictures (ignore the long hair, that's not from the fish - just some debris stuck to the glass). The photos are magnified so the bumps probably look a lot worse than they do IRL. It kind of looks like a combination of epistylis (although the bumps aren't as white as you'd expect them to be...) and parasites of some kind...? He has no other symptoms, he's active, eating and pooping fine & his fins aren't clamped. He's not shimmying anymore either (I think that was from the stress of the previous treatments). The fish in the display tanks are also doing well. The male from the previous post now also looks OK - the white spot became flatter, then turned greyish and has now almost disappeared as far as I can see. No new ones have developed. It almost looked like something burrowed into the skin and then vanished, but the fish don't have any wounds or sores, and their behaviour hasn't changed either. I haven't got a clue what this is. I'm planning to continue the salt dip & see what happens. Thing is, I can't use this much salt in my display tanks because I will pretty much kill everything So I'm now torn between running the aquariums through a UV sterilizer (attached to the filter output so it doesn't harm the beneficial bacteria), OR dosing all the fish with praziquantel as a preventive measure... do you think either of those is a good idea?
Thanks in advance, I am honestly SO confused... I really want to let the quarantined male back into the main aquarium asap, but Idk if it's a good idea given his current condition