More poo with solids is definitely normal - especially for bf babies. Soft should be ok, but hard pellets are not good. As your dr said, lots of fluids are still needed to stop constipation, and because food shouldn't replace milk at this age. If the milk intake has dropped since you started solids, I would cut back on the solids and increase the milk.

Also, banana and potato can both contribute to constipation in the early weeks, so perhaps you might want to leave these out for now until things have settled down.