Are my gerbils not friendly towards each other?

I have 2 gerbils, grey and white, and they never fight or anything. It's just that the grey one is always closing both it's eyes like it's blind and when you pet him or hold him, you can feel his spine and ribs. It seems that the white one is taking his food and pushing him away when he's trying to drink water. Then today, the white one seems to have a... Bloody hump? Hah, I don't even know. I thought it was a tumor or something. Are they fighting when I'm not looking? If they are, what should I do to stop them?