Hello, I have 2 siamese cats/kittens aged 5 months, they both have a respiratory virus which the vet says they will have for life. They are both otherwise healthy and active. Recently - 3 days ago approx one of them has had diarrhea and is barely making it to the litter tray now.. the other cat seems fine, there are no signs of worms in their faeces and their diet has not changed, apart from a daily dose ( 500mg )of L-Lysine that I have been adding to their wet food. As the other cat has not got diarrhea can I rule out the Lysine as the cause? Both cats are drinking and eating normally, I was giving them cat milk too but have stopped that now incase it was responsible, but still his diarrhea persists. Any advice please? The vet is a last resort due to the costs...