Thanks again for all the advice, I bought some l-lysine caplets as I couldn't find the powder in store but I ordered some online (way cheaper than the pills--about 2 cents per 500 mg vs 9 cents). I gave him 1/2 a caplet (250 mg) in some tuna juice since he won't eat canned. I will add it to the fountain, I don't use the filter either.
He isn't sneezing much anymore but he appears to have a sore throat as he's drinking more than usual and he was having trouble eating his usual large kibbles
. I gave him some of my other cat's food (she's on a hypoallergenic diet) which has much smaller pieces and he had no problem eating that. I'm just so worried about him as he's my baby and he's never been sick before
The vet didn't suggest I separate them but I just took in a mother and kittens as fosters the day he started sneezing and I'm paranoid about spreading anything to them. Even though they are separated I just want to minimize the chance of airborne spreading. If I had known he was going to get sick I probably wouldn't have taken them in right now