could have bumped into something, or been nipped. as far as the ich, are you sure? what does it look like? if you can get pictures of all the problems, it would be very helpful. until then,
With the Ich and now suspected fin rot i would say your problem is quite simply poor water quality. Oscars are known for being messy eaters and filtration and water changes are at the top of the list as to what will keep them healthy!
oh ok. When I first started with my oscars I had water quality issues. Guess i wasnt expecting messy to mean extremely messy. Oscars lose scales when they bump things in their tank or fight, they do grow back though. Hope everything works out for you and your O.