We've had our sweet rattie boys for 3 weeks and a day. I've noticed that they're filling out quite nicely, but have no idea how old they may be. Is there a way to figure out their ages? They're both Russian Blues and not Dumbos like the pet store claimed. Should I call them to see if there is an age record on them? I would like to know just for record keeping purposes incase they ever need vet care. Thanks