betta fix

Hi I'm Brandi I just have a question. I'm giving medication to my betta fish Sapphire and my roommates' betta fish Ricky for their fin rot and the bottle doesn't specify how many times per day to give it to them but I've done it twice a day so far, Could that be harmful to them or is it okay to...

Sorry about the bad pictures but Chester never stays still So his tail fin looks badly rotten away, as if its been chewed on and torn, at first I thought he just caught it on a decoration or something but over the last month it has gotten continually worse. His tank temperature stays at a...