There are lots of different ways that these things seem to overlap, so each of us is trying to tease out what's involved with us and our kids and then figure out what to do.
Moms deficient in vitamin A and/or folate (deficient in how much is available for their bodies to use, which can be very different from what they consume if they've got digestive/other health issues or if they need more than most people) have kids with things like tongue ties, sacral dimples, and various other, sometimes quite subtle, midline problems. A posterior tongue tie can cause digestive problems by not allowing peristalsis to start properly (have you considered cranial-sacral to help re-train the tongue movements now that your LO's TT has been clipped?), and then weird gut dysbiosis can occur, which is bad for absorption and utilization of nutrients.
Moms are rarely deficient in just one vitamin, so kids (definitely mine!) can start with a lot of things out of balance, and may be prone to the same types of imbalances as mom was, which seem to manifest more prominently in the kids than in the moms (we seem to heal together, getting clues as to what's going on from our kids and then applying them to both of us).
And we've been having cool discussions on how detoxification problems can lead to food intolerances, and again, if we've got nutrient issues to start with, at least a couple detoxification pathways very well may be involved.
I got into this (the Allergies forum) mostly due to detoxification issues (and I recognize that the leaky gut/gut healing stuff we've also talked about is more of an issue for other people than it is for me, everyone needs to figure out what their own balance is), and my kids (they're 2 and 5 now) have/had lots of nutrient deficiencies, and I think I can un-do most of the problems we've got, and ultimately be healthier and happier for having gone through this.