Red Terror. It could be either cichlasoma urophthalmus or Cichlasoma festae. Both goes on the same common name but latter being more aggressive than former. Most
LFS probably wont know the differences. There are characteristics of fish that you can find to differentiate the fish. Cant recall at the moment but will post when and if I do remember. lol!
Check out the pics of both fish for comparison. Book would probably give better/correct pics than images from googling.
Would not keep Green Severum with Festae unless in large tank, I am talking 8' or longer with densely decorated
aquascaping.
If Severum (very mild in temperment) is in isolation, try feeding better food such as live/frozen/veggies until recovers. Make sure keep your water in optimal conditions and severum should recover from injuries received from Terror. If secondary/tertiary infections take place, med as needed ASAP.
Adding salt to q/t will
minimize certain infections. Just follow the instructions on the Aq Salt box. Make sure replace the salt removed due to water changes (proportionate amt to volume of water changed).
If injuries gets worse with further deterioration of skin and/or development of fungal infection, you can try Antibiotics but try not to combine two different kind at once. Try one then others in case first did not work.
This is my crude method but have yielded great result when dealing with large fish (Cichlids, lions, Triggers, Groupers, etc). Even had good results with injection of med using hypodermic syringe.
If you have Bacitracin/Neosporin Ointment, former worked better for me though,
daily smear of Ointment have worked better and faster than tablet/capsule in the water.
Do not apply too much since any excess will just fall off (oil and water dont mix well) and end up polluting the water. If done properly, can even assist bleeding to stop.
I collect f/w and s/w fish with children for keeping in tank. Children being children, always handles fish when told not to unnecessarily. I dont use Med from lfs but depend only on Ointment for most possible infections arose from handling since yielded good results for few decades including tropical fish.
PLEASE DO NOT APPLY NEAR GILL OR AT/ON GILL.
Hope your severum recovers soon w/o further complications!