Sick pygmy corydoras

[Jaesthetic]

I decided to buy 8 pygmy cories on Sunday from my LFS and upon acclimating and releasing them into my QT tank that night, noticed that 2 were very lethargic. When I put them in the tank I added stability, stress guard, and prime.

 

Yesterday morning I saw that one had fuzzy white fungus (?) growing off of it. I immediately started treating the tank with maracyn, ich-x, and paracleanse (trio recommended by aq co-cop) following the instructions with the hope of saving the fish, if not the visibly sick one, then the others. I also put stability and stress guard in after adding the medications.

 

Today the fish with the growth died, another was belly up (though I can't find it now) floating, and the rest are looking really lethargic and sitting in the fake plants or bottom of the tank instead of swimming around like they were the first night. I did a 1/3 tank water change (added prime), then added the second dose of ich-x and maracyn followed by stressguard. This evening I put in another dose of stability.

 

Tonight I noticed that the water looks a little cloudy to me now, but upon testing the water, nitrates were <5, nitrites 0, ammonia 0. Temp is 75 degrees and I have a sponge filter and heater in there. I haven't seen the fungus growing on any of the other cories and were hoping they would be okay, but they aren't looking good despite my efforts. I have the 2 mystery snails I bought on Sunday in there as well and they seem to be doing okay although it's kind of hard to tell.

 

Does anyone have any recommendations? I'm feeling super bummed because my first set of fish that I got in the beginning of Dec were 3 honey gouramis and none got sick or had any problems adjusting to my aquarium. I got these from the same store and thought I did everything right... tried to minimize stress using drip acclimation, used stress guard/stability/prime, and started treatment before the others started showing signs but they seem to be getting sicker.

 

The only upside is that after a long internal debate I decided to set up and put them in a QT tank upon bringing them home instead of added them directly to my tank as they looked super happy and healthy at the store and I had no problems with the HGs I got from there, but I wonder if the stress of the quarantine tank is doing more harm than good. 😔

[Colu]

Corydoras can suffer from transport stress  using all 3meds at once might be to much for them  try treating with ich x frist as you have fungus problem then general cure 

[Jaesthetic]

That makes sense and I'm not opposed to it, but is it okay to stop the other two medications even after I started? I have dosed 2 days of the maracyn and ich-x so far and 1 dose of the paracleanse yesterday (tomorrow was supposed to be the second). Also, since I don't see the fungal infection on the others that haven't died yet is it safe to assume that is what is bothering them and not something else/internal?

[Dancing Matt]

Medicine can cause stress. My understanding on the quarantine trio is you dose all at once and leave for one week, don't dose again. This is a safety measure to make sure no one is bringing in disease. If a fish is having an outbreak then you treat that "thing" (fungus/parasite/bacteria/infection, best you can tell) as per instructions. My understanding is that corydoras can be susceptible to fungus (and your description seems to agree this is a case of fungus) so target treating that is likely best. 

If you are concerned about them dying, stopping could be fine for now, you would just want to watch them and if their behavior changes for the worst or they have an outbreak, that you treat them.

I would check to see if the belly up one is dead, that could lead to ammonia+stress.

Keep up the good fight. We have all had these moments. As sad as they are, what is best is to learn from them. You can become a better/more informed aquarist and your future fish and hobby will benefit.