parasites?

[Invigor]

Ok, I'm at a loss for ideas here...I have a FOWLR tank (and a few corals) 105gal tank with about 50 gal in the sump. Last week I had my koran angelfish get pop eye from scratching his face on the sand. He had been scratching for maybe 2 weeks prior to this..I wasn't sure what was up. Now my yellow tang is scratching, my maroon clown has some weird looking scar in her head (can clownfish get HLLE?), and my singapore angel has buggy eyes. I tried pulling out the koran before it died and tried medicating him with "seachem's Sulfathiazole"

Sulfathiazole is an effective and safe treatment for many bacterial, fungal and protozoan infestations in the aquarium. Usual dose is 250 mg per 40 L (10 gallons), but dose may be increased up to four-fold. Easily removed with carbon and does not impair nitrification.

He died 2 days after I medicated him. So now with 3 more fish "looking ill", what should I do? I don't have a tank large enough to accomodate all the fish to medicate them, I don't know what's causing this, and I don't know if I should medicate them all...augh.

Any help is greatly appreciated. I have a fear all my fish are gonna wake up dead some soon morning

A little reading has brought me to conclude that popeye is an internal bacterial infection. Would something like this: http://www.seachem.com/products/prod...ges/Focus.html be worth trying?