My two red nose pits whom are 21 weeks old have very soft stools. Like soft serve ice cream. Is there something I can give to to get a more solid stool. They eat Pedigree puppy food.

You can switch dog food. The pedigree is mostly filler, and often very hard on a young dogs system. If you decide to switch foods, you must do it slowly, not all at once. Start by giving 1/4 new food, 3/4 old for a few days. Then 1/2 new, 1/2 old for a few days. Then 3/4 new 1/4 old for a few days. Then all new. If they have diarrhea anytime during this process, then wait a few more days before the next step.

Have they always had runny stool, or is this something new? Have you changed foods recently? Have they recently had their shots?

Are they pure bred puppies? Sometimes that can make a difference too. Pure bred dogs tend to have more sensitive systems. Change their food to something that is made more specifically for their breed and see what happens... Be sure to follow the advise and change it slowly over a period to give their little tummies a chance to adjust.