Help!! All my fish are swollen this morning! :(

Yesterday all my fish were fine (as far as I knew) I have always changed 30-40 percent water weekly and never really come across an issue like this before. ,
Usually my water tests at
Am- 0
Nitri - 0
Nitra - 20 - 30(tap water is around 10)
PH 7.4
havnt tested my water just yet just wanted a bit of advice will test and water change very soon.
I have woken up to a dead Rummy nose, I removed him and then went to feed my fish as normal, usualy they're very hungry when I even go near the tank..for the first time in 3 years this morning nobody even remotely looked hungry and ignored the food. On close inspection half of my fish look bloated also round stomachs almost as if it looks like they've just eaten a big meal,... If this is dropsy would most of them really have it? I thought it was supposed to be not contagious... I don't really want to put chemicals in but if it gets too it I may need to. I also don't have a quarantine tank . I found this online.. Could anyone tell me what points are a good idea?


2. Create a salt bath by adding no more than 2.5 teaspoons of Epsom salt for every ten gallons of water in the hospital tank. The magnesium sulfate in the Epsom salts may help to draw the excess water out of the fish's body that caused it to swell.

3. Feed your fish antibacterial fish food. You can either purchase prepared antibacterial fish food or make your own by creating a 1% mixture of fish food and an antibiotic like chloromycetin or tetracycline.
.

5. If no improvement is seen after several days of treatment, treat the aquarium water with Maracyn Two. This medication is effective against bacterial infections and is absorbed through the skin of fish


Thanks

It is hard to say which advise is valid as we don't know what is wrong. It certainly is unusual for a whole population to get dropsy.
Photos would help.

Do a large water change as clean fresh water is a great medicine. If you don't treat your fish for worms this might be a starting point.

Have you added anything new that may have introduced pathogens or parasites? What is your maintenance schedule? What do you feed the fish? Has there been any recent stress on the fish?

Currently doing a 50 percent change now and will do another tommorow , all my levels are normal apart from Nitrate which is high so I assume this is the cause. I did miss one water change last week as was on holiday I just didn't think it would cause this much of an issue if that is the reason.
I havnt added anything new.
Maintenance is water change weekly 30-40 percent and cleaning filter and tank monthly.
Feed them a mix all foods are mixed in a jar... Flakes, pellets, algea wafers, fish crisps,..
I wouldnt say I've noticed any stress apart from today they are all majorly stressed.. Its like they have all lost their minds after the death of the Rummy nose . One of my gourami is less active than usual he is usually quite aggressive but has seemed sluggish and bored past couple weeks... I'm going to assume it's all coming from my Nitrate it is now above 40ppm maybe even 50

How old is the food mixed into the jar? I wonder about that practice, fish food also goes off and doesn't last indefinitely, and since many contain fish oils which would go rancid when they go off, I'd be careful about mixing foods up like that, especially if you end up mixing newer with older, or there's a lot more food than you'd get through within 2-3 months.

It's unlikely to be an internal bacterial or protozoan infection and unlikely to be worms.

It is either food poisoning or something in the water.

Did you do a water change or add/ do anything to the tank the day before this happened?

Do you dechlorinate the new water before adding it to the tank?

---------------------
I would do a big (75%) water change and gravel clean the substrate every day for a week.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. Wash filter media/ materials in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the lawn.

Don't add any aquarium plant fertilisers or chemicals apart from the dechlorinator.

Post pictures asap.

When you were away did someone else feed the fish? Or did you use an automatic feeder or feeding block? This often results in overfeeding which links to the high nitrates.
My advise would be to not feed fish at all when away in order to maintain water quality. Fish are opportunistic feeders and cold blooded so can cope without food for a week or two.

It's mainly the appetite Im concerned about and how sudden, they were fine yesterday and all this week. Even my bristlenose wasn't intersted in his wafer and that's saying something.
Yeah I'd probbaly say some of the food I've had for a month, some a few months or more and the flakes admittedly have had for way over a year, I didn't think it went off

Last water change was 2 weeks ago as we went away for a few days last weekend. Nothing new went in, just dechlorinator as usual, (I have always been a bit wary of dosage however with the brand I have it doesn't seem right, I'll come to this soon)
Have just don't a 50 percent change and will do it again tommorow and every day till its gone... (will this have any effect on my cycle / bacteria)??

As we went away for three days I didn't feed them, I left a few wafers stuck to the glass the night we left but that was it.

Only pictures I managed to get of bloat are these two....

.