Weight loss after recovery from sickness

Recently, one of my chinchillas had a nasty URI. He was put on Baytril for ten days. When it all started in early March, his weight was 725g. He lost some weight during treatment due to not eating as much as he should. Thankfully he was able to eat on his own for the most part during his sickness (primarily hay plus a few grams of pellets daily. CC was virtually impossible to get down unfortunately), but had to have sub-q fluids for a several difficult days when he refused to drink. His weight during the several days when he received fluids stayed around 675-685g give or take. He completed the full round of Baytril by March 20th, and began to eat and drink normally again.



However, I checked his weight today and was alarmed to see it had dropped to 620g! How can this be?? I've been weighing his food bowl since it all began and after his recovery (since I'm paranoid of relapse), and he eats on average about 20-23g of pellets a day (Mazuri) and also eats plenty of hay. Poops are normal and there's plenty of them as usual. No breathing issues or wheezing of any kind. No watery eyes. Activity seems a bit more restful at times, but that's not totally abnormal for him since I've noticed with time he goes through phases of being wild and crazy then sometimes more chill. Chewing sticks and hopping around normally from what I can tell. Anyone seen this before? Do you think that maybe he lost more weight than was evident during sickness and his weight was artificially heavy due to daily fluids?