Hi! We have had a Yellow Tang for over one year now and it has always done well in our 36 gallon tank w/ our 2 other Clown fish. Lately, she appears very stressed out or sick because her top fins look thin as opposed to being "full." 8O We are about to buy a bigger tank for her but we are not sure what could be going on with her that her top fins look so wierd. Any thoughts?!