Need help getting kittens to poop!

Last Wednesday my husband and I took in 3 kittens that were about 2 weeks old. (Posted thread "2 week old kittens"). In order to draw attention to the specific issue I am having though, I am making a new post.

We have been stimulating the kitties to get them to pee and poop after each feeding. For the first couple days they were pretty regular with peeing every time they ate and pooping once a day, a couple days they pooped twice. On Friday and Saturday, we found poop on the blanket they have in the bathtub we have them set up in so one went without our help but we don't know which one....we have an idea though.
They all grey one poops for us and has (from what I have read, normal poop) at least once a day. One of the grey/white ones poops for us also, same as the all grey one. The third kitten is the runt of the three, smaller, eats less, when we got him seemed in worse shape then the other two. His behind area is always wet and scraggly looking-but we realized that the other two kittens try to nurse off his behind, and he has peed and pooped in the tub from that. However, since finding poop in the tub yesterday morning, the other two have pooped for us and the little one has not. We try to stimulate the area using a warm wet washcloth but he just cries when we do it. His appetite is still normal but I am worried about him not pooping again yet. Also, is it normal for the other cats to only go once a day? They are still on only kitten milk replacement from the petstore, but is there anything I can add to it at this young age to help them poop? I am trying to avoid a vet visit since they are so little but if I need to take the little one I will.

They all have their eyes fully open now and weigh right about 10 ounces. We are not sure of the age, but their eyes just fully opened within the past two days.

The only way I can get small kittens to poop is by holding their bums under a warm running faucet. For some reason the washcloth method never worked for me.

I tried running his backside under a trickle of water and that didn't make him go either. One went yesterday morning but that was all for yesterday. I think when the can of powder we have runs out, we should switch back to the pre mixed cans of formula. Does anyone know if that would cause constipation? From what I have read, the powdered kind can cause constipation over the pre-mixed?
We went w/ canned powder because it seemed more cost efficient and I wasn't sure what the difference was.
Anyway, this morning on their blanket their was a small piece of dark brown poo, it was hard and a small amount bigger then the size of the nipple we feed them with. I think it was the small kitten because it was hard like it had been stuck? idk. Sorry for all the poop talk! haha. I just wanna make sure they are healthy and doing well. I was thinking about introducing a tiny little box w/ some litter to see if they are ready for it. I watched one of them kinda squat and pee yesterday on their blanket without being stimulated so I wasn't sure if it was worth a shot to try this early or not.

"I think when the can of powder we have runs out, we should switch back to the pre mixed cans of formula"

Yes, it may be worth to swich. Cats are individual.

If you can get goat milk, it is perhaps even the best, although so "primitive". More than one rescuer, who used goat milk in dire emergency as there wasnt anything else - did proceed with it also after returning home... There is Forumite Calico witnessing in a neighbouring thread.
http://www.thecatsite.com/forums/sho...d.php?t=231989

Do you know about the site www.kitten-rescue.com, by our veteran forumite Hissy? If not, look in there, you will surely get more than one tip.

Good luck!

For my non-poopers, I add a small amount of (light) karo to one or two feedings to help get things moving. Karo is safe, and is included in many home-made kitten glop recipes.

Also, if the siblings are nursing on the runt's backend, they should probably be separated. Not only is it gross for obvious reasons, but it can also damage his genital area, and it may already be sore, since you said he cries when you try to stimulate him.