I've been taking care of 4 stray kittens for almost 7 months. The smartest and most sociable of them all which is also my favourite is missing since a day ago. I saw it 2 days ago, it looked tired and not well in the afternoon but did get up and walk. But by late afternoon, it looked like it was much more lethargic and probably peed on it itself because its paws were wet and covered in dirt. Its eyes looked infected and it had discharge from its nose. Wasn't eating and drinking either. But its sibling displayed lack of appetite and nose discharge last Friday and it's up and running since Tuesday. Another sibling is also unwell and was missing for one day. I should have taken this one to the vet but I just thought it may recover because it looks the kittens are have some sort of cat flu. They are older kittens but still - should I be worried? It would be quite painful for me if this one dies because it is the most liveliest and the one who alway has good survival skills and the one who approached me first. Could it be poisoned?