So today I ended up taking my rat Whitechapel to the vet, thinking he had a respiratory infection. He had porphyrin around his nose and every once in a while I would hear a sneeze so I was super worried. Turns out he is actually pretty healthy, the vet thinks that he is stressed, not sick. She also noticed that he is missing fur on the end of his scrotum, the part farthest from his body and the skin is slightly inflamed. There was no blood or anything, just irritated skin. Since he is perfectly healthy besides that she thinks that my boys might be playing too rough. Whitechapel is my most laid back out of the three of them, and doesn't want to constantly play fight like the other two. My other rat, Codsworth is a lot more energetic than him and is usually the one to start any play fights. I'm pretty sure they're just playing, I've been checking for scratches just in case but there is nothing. I got the three of them two weeks ago and I think that they're around 8 weeks old. They seem to get along fine, and I always find them cuddling together, so I don't know what's going on. I'm concerned and want to get on top of this issue before it potentially escalates. I went out and bought extra toys to hopefully keep Codsworth more entertained and have been trying to get them out of the cage more (only Whitechapel will walk on the floor without freaking out, I'm working on the other two). They have no food aggression or anything, they are fine sitting on the dish together when they eat/drink. When they get treats I give them one each individually so they don't fight over those either. I don't have a picture, Whitechapel isn't comfortable with being picked up and I don't want to stress him out more than he is after going for a drive to the vets today, but I will try and get a decent picture as soon as I can. The vet said to watch them and interrupt any play fighting that looks more harsh than usual, and that if it gets worse I'll have to apply topical cream to Whitechapel, and potentially separate one of them (if that happens I will get another rat so they aren't alone). Does anyone know how I can try and fix this? I didn't have this problem with my previous rats so I don't know what to do, but I want to nip any potential bullying or aggression in the bud. Any advice would be greatly appreciated!