Having Problems with 3 men.

I have three male chinchillas. They are all usually fine, I let them run around my room for a long time then I have cages for them to go back into to eat, sleep, drink, ect. The cages are just left open so they can run around my room again if they want to. They are usually fine, but the past couple days they have all been fighting really bad. My oldest chinchilla had the tip of his tail bit off and blood got everywhere. I watched them for a little bit and they kept attacking him. So I put them all in separate cages to give them some time apart. My second eldest got out and somehow got into the same cage as the eldest and had him by the throat with his teeth. I completely separated them now and they aren't even by each other.

I've looked up a lot of different sites and some say they are in heat and fighting due to hormonal change and dominance. If so, how long should I keep them separated for before I try to re-introduce them? How often do they go in heat? Will I have to do this every time they go in heat?

And now my oldest is real jumpy and bit me twice when I tried to calm him down. His tail is still bloody and he won't let me touch it. Should I do something with him?

My youngest one doesn't seem any different. Is he not in heat? should he be fine for now?

Please help