diarrhea

i have 2 cats ages 11 weeks (Gilbert) and 9 weeks (Zoe). this past friday I took them to the vet for 1st shots, dewormer and flea treatment. since then Gilbert has gone from spunky playful kitty to a sleepy doesnt want to play thin kitty. his eyes are clear no 3rd eyelid but he is having diarrhea so much that i dont think he can control it. he has gone poop under my sons bed a few times. even tho the litter boxes are both clean, and in the same central location that they have been. Zoe on the other hand was infested with fleas when we took her in and since the appointment had perked up and is the main cat on hand now tho still a huge sweet heart.

my question is would the Vaccines have caused this or could it be the dewormer still messing up Gilberts tummy?

both cats were given the exact same meds, same dose, same day. 

Thanks

Vaccines often cause cats to be a little "off" the next day.

I'm not sure, but I would think dewormers would mess up cats' stomach if they are predisposed to that.  Every kitten/cat is different--as your two cats prove!

Is Gilbert still eating?  drinking water?

Gilbert is still eating and drinking. I only give them dry kitten food but I've read on here that that can mess with their tummy. Should I maybe try some wet foods?

It is hard to know exactly why he has such bad diarrhea.  Has it decreased any?  I wouldn't switch foods right now; change of food in and of itself can cause stomach upsets.

If his diarrhea persists, I'd call the vet, especially if he is losing weight.

Once his diarrhea is lessened, I would consider transitioning both your cats to wet food:  wet food is better for kittens/cats than dry.