please help me out

I've looked everywhere online but can find a thing, so hopefully someone on here can help me out.
I have 3 guinea pigs, and two always fight. And they're not play fighting (atleast to my knowledge), one has seriously got injured several times and we have tried separating them, but it never helps. Right now, I'm really worred since one of them is shaking and drooling excessively..after a big fight of theirs. Is it because of the heat or something else? I'm really worried and I need a solution. My familys thinking of selling them and I don't want that to happen. Thanks.

Sorry if that didn't make sense I rushed to write this. If you don't know how to help, dont respond to this.