She may be allergic to something you are feeding her. Allergies manifest in different ways --- some develop hives, or vomit, but others develop a rash in their bottom. May or may not have, but just a thought.
Regarding the bowel movement, it is related to eating solids, in general. Especially right now that your child's digestive system is learning to cope with these new substances. What she passes are things she doesn't need as of the moment. And at this age, they get most of their nutritional needs from your breastmilk still, so they get rid of the other stuff. Anyway, solids at this stage are pretty much practice for right now.
It also depends on the person how many bowels they have. My little boy still has 5-6 a day also, and he is 1. But then again, he used to go even more frequently when he was younger. Yur ped was right to say that as long as it's not watery, or even that there is no blood in the stool, you don't need to be concerned.
Ooh, and maybe, don't use Aquaphor, since that is mainly useful for dry skin --- and not only will it slough off the outer layer of skin, it will keep the moisture that's already there flush with her skin --- thus aggravating the redness. Desitin original and A&D are better at protecting and healing your child's skin from the rash.