help bala shark

Purchased a bala shark from an lfs about 2 months ago at about 3 1/2 inches and he was already big top to bottom and now hes pencil thin. Hes the first one at the top eating and going crazy always and swims alot hes with small GT, 2xEBA and 2xFM cichlids a pictus cat and 6xlarge black skirt...

Dear Guys, I just got an aquarium few days ago its 3 by 1 ft pictures attached. Today morning just saw my bala sharked has a injury on the left side as in pictures idk what or how did he got it but it has stopped eating and kind of feeling stressed aftter looking closely it looks like it has...