I would like to suggest that one "treatment option" is to not add too many things or make too many changes at once. These kids can react so individually and differently, and a "throw everything but the kitchen sink" strategy can result in a confounding "who know what is causing what" situation.
For example, in some (rare?) cases, vitamin D makes some kids worse. That is even when they might be low on vitamin D in their blood - go figure (and some have went and figured, and have explanations for this kind of paradoxical thing).
Somewhat less rare (in my humble opinion) but still rare, are kids that get worse on probiotics. Our son was measurably worse (I keep track of daily soap use as a measure of his OCD) on many different probiotics. Some kids react strongly to some probiotics, some parents mistake that (in my opinion) for herx, and some (such as my son) get mildly worse on probiotics. And of course, many have no problem with probiotics. But if you don't introduce them separately (i.e. have them on it for a week before abx), you won't know what is doing what. You can also try to figure that out by removing things later. There is more than one story of a mom that in desperation (when her child was not improving) took the child off everything - and the kid got better. But again, you won't know what was the culprit unless you remove one at a time, wait and watch, add back in, wait and watch, remove again, wait and watch, remove another, wait and watch, etc. It is a long road, and also a less-travelled path (because we can't be patient enough - we want a quick fix).