Sick kitties?

So my 6 month old kitty just walked into my bedroom, looked at me, let out a loud "something's wrong" meow, and threw up his lunch. Also, for the past couple days, my 8 month old will wait until I'm cleaning his litterbox or in the bathroom (where one of their litterboxes is) to jump in his litterbox, look at me, and have (extremely smelly) diarrhea. I know he only passes runny stools when I'm watching because I check out the bowel movements when I'm cleaning their boxes. So it seems like they want to tell me something by waiting to have these episodes until I'm sure to notice. The thing is, I have no idea what could be making them feel bad. I give them revolution monthly, which should take care of any roundworms, and they've both been treated for tapeworms. Could it be something bacterial making their stomachs upset? How would a vet check for this? Should I bring in stool samples? I'm going to take them to the vet tomorrow, but I'm not sure what to have them checked for.

My first thought would be if you've changed anything recently... their food in particular. But I'm sure you would have mentioned that. Any new treats? It does seem like something is going on with the poor babes!

could it be the worm treatment ? Apparently it does clean them out a bit.

I would take a stool sample to the vet. Throwing up the occasional lunch isn't really that strange (my adult cat occasionally overdoes his dry food and then throws it up once it swells up in his tummy), but diarrhoea doesn't sound too good. Let us know.

They were both wormed quite a while ago, so I don't think that's it. I do give them a varied selection of wet foods (but that's nothing new), they're still getting the same dry food and treats. I've been racking my brain as to anything they could've been getting into. I don't have any plants or anything, but now I'm starting to suspect that they may have been pilfering milk from my cereal bowls in the mornings. I'm usually running late and end up just throwing the bowl in the sink so it's very possible they could've gotten into the leftover milk. Does that sound like a reasonable cause for vomiting and diarrhea?

I dont know much about eating left over milk by cats. But I am pretty sure left-over milk can be bad for anybody, or any kitty. Not serious bad, just a little sick bad.

And the poop and the throwing up sounds like that that might be it. I wouldnt worry all that much, in a day or two if they are still sick, I'd call the vet.