I am a first time rat owner. I got two baby male rats a little over a week ago. Their testicles are noticeably larger than they were a week ago. I can’t help but notice that one of my boys has only one testicle. Has anyone else had this happen? Is it a health concern? And, should I take him to the vet? I am concerned that a vet visit could be very expensive. I don’t want to spend a ton of money to find out that he is okay.