lethargic kitty

I have a kitten who is just over 3 months old, and in the past day and a half he has barely played at all. Usually he sleeps for an hour or two (or three, depending on how tired he is) and then plays like mad for another hour or two. But in the past few days, he hasn't even gone crazy in the evenings like he has every night since I got him in mid-July.
I think it might be because one of his eyes is infected (it was infected when we got him, we treated it, and when he got his vaccines our vet told us that the infection might come back because of that) but we've been treating it for the past week, so it might be that he's just not in the mood, what with an infected eye and everything. Another possibilty, which my dad (who has had dozens of cats because he used to have a farm) suggested, is that he is going through a growth spurt. His feet have recently become pretty big in proportion to his body, like a puppy's, so that's why my dad thought of that.
Basically, I just want to know if I should be concerned about his lethargic behaviour or if it is, like my dad thinks, just a growth spurt and to be expected. Although I don't know how much faster he can grow, he gained almost a kilogram between getting his shots on August 14th and his last vet appointment on the 28th!
Anyway, any advice, suggestions, whatever, is greatly appreciated (as always)

-Liz

I personally don't think a growth spurt would cause lethargy. I would be concerned that there was more going on,especially if you have been treating the eye infection for that length of time and the lethargy just began! If you've been using eye ointment,he may need to be put on oral antibiotics or be treated for some other ailment. I think I'd be taking him back to the vet.

I, too, recommend Veterinary attention. Let's move this thread to Health

Is his appetite still good?

yep, he's still eating normally. We had to put him on oral antibiotics before for an upper respiratory infection, and that cleared it right up. right now we're just treating it with an ointment.
i just got home from work, though, and he's wide awake and alert as anything, playing with (by the sounds of it) two toys at the same time. but if he goes back to pretty much constantly sleeping like he was before, i'll definitely take him to the vet on tuesday...monday's a holiday so the vet won't be open. hopefully he was just really tired for some reason! *crosses fingers*

thanks for your replies though! taz appreciates them too - he's reading them now.

-Liz