Dead Peppermint Shrimp

[StrongBad]

So I got 'Pepe' a week ago and drip acclimated him. He seemed to do just fine. He molted a day after I put him in and ate the flakes and stuff that I target fed him. Well yesterday morning I saw him and he was alive but looked a little lethargic. Within the hour he was laying on his back not moving. The only thing that I can see might have happened is that the water temp dropped from 80-81 to about 76. Would this temp swing have caused his demise. My Ammonia, nitrites, nitrates are 0,0,5. Calcium 420, no phosphates, ph 8.2.