Came home, saw this:


Fin rot maybe? The clown is in a 125g with 2 plecos a BGK and other clowns. I bought a 210g for them, but had to move their 125g so the 210g could go where the 125g is... so on Sunday, I moved their 125g and put them back in it which I am sure caused some stress - but I haven't moved filters or anything over yet so the BB should be fine.
Ph 7.0
Ammonia 0ppm
Nitrite 0ppm
Nitrate 10ppm
Used API test kit
Help please!