M.C.
It sort of makes sense. It takes about 20min for food to really start getting digested. I would look at the ingredients of the solids. Its possible that there is something in there - whey, wheat, milk, carrots, pears, peaches - that she is having a reaction to. Which would make sense also if she had MORE problems while you were breastfeeding.
I would also consider contacting a pediatric allergy specialist to see if some blood-based testing can be done.
M.