The only way to improve their care is more water change, better feeding and remove many of them. I think this will need involvement of the management staff, so I would think you should talk to them first. If they are not amenable to take better care of the fish, you may possibly hinting that you may:
-write to the local newspaper
-inform some animal right group
-....

FWIW, even at the Dallas Aquarium, the fish in some of the display tank are sick with deformed fins and HILLE.