Help!! BTA help / concerns.

I recently purchased a bubble tip from my lfs and it was a bigon. Got it home and drip acclimated it for about two hours and placed him in the tank with lights out. The next evening I noticed a tear in its foot so I kept a close eye on it.

It split, two nems for the price of one! I was excited that I got to actually see the split, but also a little concerned it split so soon. I would assume from stress?

Well this holiday weekend I went out of town... I just got home and noticed that my nems are pretty shriveled and don't look so hot. I did some research on nems that are on their deathbed and the number one sign was its insides spewing put. Mine don't have that. Upon further investigating I noticed I now have THREE nems. One of them had split again while I was away. I checked my water parameters and I do have a semi high nitrate level sitting about a 15-20, other than that everything is in check. Are my bta on their deathbed? Recovering from splitting that much? I did also notice that after rearranging cords on my timer for the weekend, I did forget to plug heater back in so my tank is at 71-72. Could they just be "cold"?
Any advice would be awesome!
Attached is a picture of two, I csnt get a picture of the third as he is hiding in the small pass through.