Thank you so much for your fast reply. I appreciate it so much that you're here to help me out!
I'm aware that my tap water might not be suitable for Mollies anymore, and I will look into relocating the fish later, but right now I really just want them to survive
((
Answering your questions :
I did treat with API super ick cure (picture attached). I treated with one package per tank. I have a 20 gallon tank (about 18g volume) and I used approximately half the dose (=1 package) because I am currently homing a loach from a friend in the tank to help with the snail problem, and it said that for scaleless fish use half the dose. So, one package, after 48 hours another package, after 48 hours 25% water change (which is today). Carbon filter was removed.
Before starting the medication, I did 50% water changes every 1-2 days.
Pictures of the fish attached. I'm bringing the GH up to 200 with calcium chloride and magnesium chloride. However, that issue should only apply for mollies, and now the first white clouds are showing symptoms?
Only the first molly that I reported sick had grey patches. The other fish "just" have dissolving fins, no patches.