Fin rot commonly follows ich, especially if they are sensitive or were sick for several days. I recently treated ich on guppy fry who had lost most of their fins due to subsequent fin rot.
Now, I've never kept clown loaches but keep him good and warm but not uncomfortably so. I treated my fin rot very well with melaleuca oil (marketed as API Bettafix), and non of my invertibrates died. Methylene Blue is the old fashioned go-to antifungal if you know how to dose it correctly.
Good news is most fish recover well from fin rot if caught in time.