What you're describing sounds more like intolerance to me than allergy, which would probably also come with something like eczema; intolerances, though, often show up as problems with digestion. (That's oversimplifying but it's helpful when first learning the difference.
Cauliflower is a brassica/crucifer and can be hard to digest, like cabbage and broccoli; may want to back off on that one for a while.
Smelly poops like that would be a sign that the food isn't being digested well. If you can find probiotics, they can help to give the gut the right amount of "good bacteria" to help with food digestion and nutrient absorption. This is especially important if she (or you, as you're BFing) has been on antibiotics at any point, as they would kill not only the harmful bacteria causing an infection but also the beneficial ones in the gut that are so very important to digestion.
As an aside, swedes are what we in the States would call turnips, and courgette is zucchini.
