Ash F

My favorite way to get good fish pics is to actually take a video with my phone and then pause it on my computer and take screen shots.

Apologizing in advance for the amount of detail, but I am really hoping to get this right and stop losing so many fish. I am struggling with my panda cory's that I have had for a few months. I have a 32 gallon fluval flex with an additional sponge filter and air stone with 6 male endlers, 1 Siamese algae eater, 8 mystery snails, 3 nerites, and now 5 panda corys. I feed a variety of foods - omega one sinking pellets, hikari crab pellets, hikari fancy guppy food, frozen - daphnia/brine/worm variety, home made/crayfishempire snello, occasional algae wafers, snail cookies, calcium chips, mineral junkie bites (no one likes). I recently treated for gravel worms with expel-p and cyanobacteria with erythromyacin and then had a diatom outbreak and didn't know about phosphates. I got a phosphate testing kit after losing a betta and the levels were at 5 (he also appeared to have dropsy, but was maybe 1.5 years old at the most). I added phosguard and the levels are near 0 now. I have quite a few plants and use the liquid green and now under gravel tablets from aquarium co-op. I didn't realize until reading recently that I should have removed my purigen when treating for the worms/cyanobacteria and that is still in the filter. I also have switched my substrate from gravel to black diamond blasting sand after struggling to keep my nitrates down, for aesthetic reasons and for the cory's thinking it would be better. I gravel vacuumed sections and removed it gradually over two days and then added in the well-washed sand. I woke up two days later to a dead cory (which appeared normal except for some red blotching near one gill) and now one cory a couple days later has a white nose. It doesn't look fuzzy, but looks more like decay/rot/transparent? Last night, I added some almond leaves, fritz 7, stability, stress guard, a wonder shell and have been doing daily partial water changes since changing the gravel out. The panda cory looks a little worse today, with the white moving up the side of her face near her eye now. There has been a small ammonia spike and I am using prime/water changes to keep up on that daily. There are still nitrates present and up to 40 ppm. I am thinking the panda cory is struggling because of the nitrates/maybe has an injury/stress from changing the substrate, maybe the substrate is too sharp. I don't think she is eating. I am not sure if it is columnaris, mouth rot, an injury, an infection post injury. I am new to corys. One fish store recommended sulfaplex or kanaplex, but I am worried about the nerites. I have a hospital tank, but worried about the panda cory being alone, and for how long? and what treatment option would be best? I currently have kanaplex, sulfaplex, neoplex, API fin and body cure, API fungus cure, maracyn, expel-p, jungle fungus clear, and stress guard. I can go to the store later today to pick anything up that could be helpful--medications/softer sand to cap the blasting sand, or anything else that might be helpful. Even open to getting a second aquarium set up if need be. Looking for recommendations/advice. I also feel like my tank is overstocked with so many mystery snails, but I enjoy them. One of them is floating and I have been giving her air baths for the past week, another one gets regular air baths because he is always upside down and always has been (genetic issue?).