We just noticed that Pan's been sleeping all day today, in contrary to her daily routine of bugging everyone, running sideways and just constantly eating. Today, she seemed low energy and wouldn't eat. At first I thought she have an appetite but later realized that it wasn't her finishing her food but Lotto. She's also warm to the touch and always curled up on bed. I fed him with ID, a prescription diet for kittens with intestinal issues, or fed to kittens that have no appetite. She did finish the serving and we were quite happy. She seemed very weak, probably because she didn't eat the entire day. I gave her a dose of vitamins too, to boost her immune system (she actually takes it everyday since she came here). I'm hopeful that it's nothing. We have experienced this with our previous rescues, Annie and Nikki, where they just lost appetite and became lethargic and lymping. We both took them to the vet for examination and the vets didn't find anything. They eventually regained their strength and now happy adopted cats. I hope it's the same case for my Pan.
If there will be no improvement tomorrow, I'll bring her to the vet.