It was probably water weight. When they hold water or are well hydrated they appear bloated. Your pac probably urinated after getting out of the water. They usually urinate in their water but sometimes do after coming out or when they're startled. Like toads do when you pick them up. The temps are definetly too low for one that young. Even adults need very little fluxuation between daytime temps and night time temps. High 70s at night is an ideal temp and day should be no higher that 81 or 82 for one that young. To much temp fluxuation can cause stress. Hope the little guy/girl eats for you soon. Don't for get humidity. 70 to 80%.