Hello all. I am new to reef central and need some veterans advice. I have a yellow tang that I have had for about 1 year. Over the past 2-4 weeks the dorsal fin has been "eroding", it has white around its face and near the tail. I also just noticed some very small faint red spots on the tips of the dorsal and on the fin underneath the tail (unsure of name). This is my first tank and it is a FOWLR 30 gal with 3 clown, yellow tang, star fish, cleaner shrimp, and 5 snails. I do water changes every 30 days. Have a penguin 350 biowheel filter and 2 200 gal water jets. Attached is a picture. I need advice before its too late, any help wiuld be appreciated. Thank you!