I just started breeding rats I have 4 colonies with a 4 to 1 ratio per tub. One tub is an established colony and the others are first time moms. I have had about 4 litters and it seams like a lot of baby's are dieing. The established colony has 2 litters in the tub and out of 22 baby's 5-6 have died and 3-4 out of the colony with the first time mom is the a normal death ratio? Also some of the new baby's look like they have cuts or there skin was pulled apart on birth they are not bleeding the skin is separated in parts what is this. Any help or tips would b great thanks!