if he still looks and appears healthy, i wouldnt take him back home just yet.

i've always had great success with brained f/t pinks in a delicup for young corns. so maybe try that.

is there any change that has occured other than the slight change in temps? i dont think the temps would throw him off, but something like extra bright lights for long hours or seeing a lot of people (if it's on display) might stress it.