Help pls!

[Jenaliff]

Okay, so I bought a pictus catfish to add a friend in with the one I already had. I never quarantined him like I should have and soon noticed white spots sticking off of him. Suddenly my other catfish had it too, so I took them out to quarantine them and treat them for ich. Well, they both died a couple days later. So I go back to my original tank and notice half my other fish have white spots and what looks like fin rot. I tried to treat the whole tank with a couple different treatments for epistylis and fin & body rot (not at the same time), but still ended up losing most of my fish throughout all of that!
I'm at a stand still.. I just did another water change last night but other than that I haven't tried to treat anything for about 2 weeks. My dojo loaches are doing fine and my snails are doing fine, but I added 2 platy babies 4 days ago (because I have like 40 and counting) and I think I'm noticing spots on one of them already. I can't get good enough pictures, but I'm just not sure where to go from here.

 

[AdoraBelle Dearheart]

Please don't add more fish to a tank that has a disease!!

Enforce a quarantine on that tank, don't move fish to or from, and ideally don't share equipment between that tank and any others you have.

Can you share some clear photos of the tank and fish please, or you could take a short video showing them, but be aware that the video upload feature doesn't work on this site, so it would need to be uploaded to youtube then shared here.

Please copy/paste and fill out the template below, the more info we have about the tank, the better the chances that someone will be able to help. For example, it's possible to treat ich by using a heat treatment and raising the temp to a certain level for a fixed period of time to kill off the ich without killing off the fish, which is more effective and less stressful for the fish than a bunch of different medications that may not work. But first, we need to make sure that it's ich you're dealing with, and if there are other issues contributing.

My additional question: Aside from the pictus cats, how many other fish have you lost? When was the last loss?
Template with emergency questions to copy paste and fill out:

Tank size:
tank age:
pH:
ammonia:
nitrite:
nitrate:
kH:
gH:
tank temp:


Fish Symptoms (include full description including lesion, color, location, fish behavior):

Volume and Frequency of water changes:

Chemical Additives or Media in your tank:

Tank inhabitants:

Recent additions to your tank (living or decoration):

Exposure to chemicals:

Digital photo (include if possible):

 

[Lajos_Detari]

Can you show us some photos of the sick fish?
Without any photos, we can't identify the disease.

Can you share with us what medications you used and for how long?
Most parasites treatment will need at least two weeks of treatment or more depending on the types of parasites.

Ensure that you don't overfeed especially for Epistylis.
Epistylis can kill quite fast unlike Ich.

Also, ensure that your water quality is good (free from Ammonia and Nitrite).
Bad water(with Ammonia and Nitrite) will lower their immune system and promote the parasites and bacteria growth.

Here are some info about Epistylis.
Make sure that you diagnose correctly and it's not Ich.

10.2.4. Epistylis in tropical fish

Epistylis is a very common and very unrecognized fish disease. It is commonly confused with ich.

aquariumscience.org