Teeth Loose?

i've had this happen already before, everything turned out just fine.. but now it's becoming a regular thing. He's Lost a tooth before. No causing factors, he has not fallen He hasn't done anything out of the ordinary, He has a balanced Diet of Veg. And pellets. I don't know why this would happen. you see, I was having some off color on his bottom teeth, Which has since gone away. But now he's got a loose tooth again it's the same tooth as last time. I am worried that he is hurting himself. Any tips?

Thanks!