Any other solids then? If those are the only two, I'd back off both for a bit till the tummy recovers, then try a bit of one and see if it recurs. It might also be a matter of a digestive system needing a bit more time to mature, too.
One other thing to try is infant probiotics; if the gut flora has been disrupted, then pretty much everything is going to be harder to digest than it otherwise would be. Note: infant probiotics are different from adult probiotics (which I didn't know when I gave my DD#2 some of my adult ones); not the end of the world, but there is a different set of gut bacteria in there as babies.