Thanks for updating us Casey and the information supplied.
Sad to say but ending up with a healthy 1.7 out of a 3.12 from a pet store is actually pretty good odds for pet store rodents. Back when I was buying a lot of breeders out of pet stores it was sadly common to loose an unacceptable amount of them to illness, stroke, failure to thrive, etc. Once you are enough generations away from the pet store you'll find your home raised feeders & breeders to be far more stable healthwise.
Heck I remember talking to Becky on the phone, asking her a question about a rat and another rat literally fell over and died right in front of me. Not real signs it was critically ill other than some fluffed fur and that fact that the other rats from that recent purchase seemed to avoid it. Then bingo...flat out dead just like that.