Two male dogs fighting, female puppy introduced three weeks ago

I have two neutered male dogs, one is 2 one is 12, they’ve been together for about a year and a half, became pretty close playing with each other a lot. I recently got a female dog, unspayed 4 months old. The two males have been fine for the 3 weeks I’ve had her and suddenly they can’t even look at each other for a second without breaking into a fight. Female dog is not in heat if that helps. They all stay in a room together when I’m at work and I will watch a camera, no fights break out and they all mind their own business but I just don’t know what to do