Mine are about a month apart in age, but the breeder I got them from kept them together after they were both about 1.5" and Peut had a missing foot when I got him, but after I put them in their 40 gal they have now, they have not had any problems.
But I know that's not the case with everyone's lotls! Especially if they have smaller tanks and less hiding places. I think that's a big factor of it.