The past couple of times that I've bought cories from the LFS they've come down with fungus. I've always foud them to be hardy fish the past so I'm not sure what I'm doin wrong all of sudden. Fish are quarantined in a barebottom 10gal with a seeded sponge. I'm using Parasite Guard to treat without any luck. WCs are 50% every other day. Better advice for treatment?