I Found Poop!...But I Have Questions....

This is the first time that I have found any kitty poop. It was in the blanket that they sleep on. I am ASSUMING it is from one of the kittens because it is kind of small to be mom's. It did seem rather firm, not soft, so could that be a sign that they may not be getting enough liquids? They are still nursing, they will be 5 weeks on Sunday, and they won't even try the soft food, though one of them DID take a few bites of the hard dry food.
Another thing is that I put it in their litter box, but mom went in and took it out. Didin't do anything with it, just used her paw to uncover it and put it out on the floor.
Any ideas? Or is this normal?

3-5 weeks old is around the age I normally discover kitten poop. Healthy kitten poop should be solid. I would place a small litter pan near by that they can easily get in and out of. I have no idea why mom would dig the poop out of the litter pan. I would put it back in the litter pan to give them the right idea.

You can try mixing the soft food with baby food to get them eating. I usually put a little canned food on the roof of their mouths to help get them started. Often with that little help, they pick up eating wet food quickly.