I am really struggling with my little double rex hairless Izzy. She seems great. She popcorns more than any non-baby rat I've ever seen. She plays. She cuddles. She explores. She eats great whenever she gets the chance. She has no sign of tumors, respiratory distress, or parasites and she never has! But she will not grow. She was 5 wks old when we got her in April and the babies that were born in July are already bigger than her. Also I can't seem to keep her rounded out, I feed my hairless rats multiple times a day because of their fast metabolism, but still if I miss even one feeding with Izzy or if her cagemate Clarice gets more of it you can see immediate noticeable weight loss. Then I spend the next week trying as hard as I can to put weight on her again. I've had a stool sample looked at and it was clear. And her cagemate Clarice (one of the July babies) is growing like a weed and looking great. What could possibly be keeping my little Izzy from growing and maintaining weight?