-i personally would not jump to treating with meds yet (especially with a gar that small). i would raise up the temp to 78-82 and do 50% water changes daily and see if anything clears up. a photo would help with figuring out if the fish is actually bloated or if it is just stuffed from food, etc. gar waste material can be multi-colored at different times, so again, i wouldn't jump to meds or that it's parasites just yet.
also, most of those tankmates are terribly inappropriate for gars...separate from the catfish hybrid and from the pleco. rosies will be ok as they can be food for the gar. also, unless you caught the gar on our own outside of Florida (and assuming you have ruled out LNG/SNG/ALG), it is highly unlikely the gar is a spotted gar but more likely a Florida gar (look very similar).
good luck with your fish, and keep us posted on its progress--
--solomon