So I woke up and checked on my fish this morning and 1 of my danios appears to be missing an eye. He's been in there for over a month. Water parameters have been 0-.25 ammonia, 0 nitrites, 5 nitrates. I just did a 50% wc last night tank mates are 5 glass catfish, 1 bn pleco, 4 other danio, 2 kuhli loach, 1 mystery snail, 1 dalmation Molly, and 1 swordtail. No one seems to be chasing him or anything and he is still active but seems off balance. Only thing I've done different recently is dosed some flourish for my hornwort.2 capfuls for 30 gals. Not sure what type of danio. They're greenish Orange with a black stripe. Please help. Thanks!