Sick Panda Cories - Need help with illness ID

[Spur]

I've been going through a lot of google searches to try and find what this illness is and I haven't found any solid diagnosis. I have ideas, just not positive and I want to be sure before I buy the meds.

First, I want to say, that over the last month, the aquarium was treated for Ich. I got some clown loaches from PetSmart and they had white spots on them within a few days, whether it came from my tank or not, I'm not sure. This has led to all kinds of stress not only for the fish, but for my GF, it's her tank and she hates to see them like this. The Ich has been treated, raised temps to 86 for 2 weeks and treated with paraguard and stressguard for 3 weeks (while heat was up). During this time I never saw white spots/ich on the cories, yet they would show signs of stress quite often by rubbing on substrate/driftwood, etc. They'd swim around in their groups sporadically in the upper part of the aquarium, as well, which was unusual for them.

Anyways, it's been a week at least since the Ich has been treated, the temps are back down to their normal level (78 Degrees). A day ago a golden longfin danio died - of what, I don't know. It had really red gills and it's body was slouched, it happened pretty rapidly. None of the other fish in the tank are showing any signs of stress at this point, other than the cories. Only one of which is actually showing any issues with it's skin, odd discoloration.

Ammonia: 0, Nitrites: 0, Nitrates: 15ish, TDS: 250, Ph: 7.6, Water changes quite frequently 30% or more every other day, tap water treated with Prime.

20 Gallon tank, black blasting sand substrate, aquaclear 50 and sponge filter, live plants. Tanks been up since early September. Tankmates are Dwarf gourami, longfin danios, longfin bristlenose, clown loaches, and rasboras. They are fed a wide variety of food, shrimp/spirulina pellets, flakes, frozen brine to daphnia, o-nip.

We don't recall the cories having any of these problems prior to the clown loaches and the ich incident.

Here's some photos of the fish in question. I'm new here guys and hate to join under these circumstances, but I've searched the web and this site seems like my best shot of getting results for these lovely little guys. Thanks in advance, much appreciated.

[gasmaskdude]

In my experience it looks like a bacterial infection arising from the stressed cories, the temperature increase may have triggered this. Is it a white film growing on the fish? I recommend quarantine and paraguard treatment.
You can do a salt dip, that may help a great deal but it can also shock the fish sometimes.

[Spur]

I've been treating the tank with Paraguard for a month now, so that's not helping. I did ask the owner of the LFS and he did say it looks like something bacterial as well and suggested I try Melafix.. so I'm dosing that now, we'll see how it goes. We've added salt to the tank here and there. From certain angles it kind of does look like there is a white film growing on the fish. I don't have an extra tank to quarantine so the whole tank is going to be treated. Thanks for the advice.

[gasmaskdude]

I highly recommend getting a bucket or some plastic bin and set it up as a quarantine tank, it will help them recover better and not unnecessarily stress the rest of your fish