When my son was having a lot of difficulty with speech, I started him on a probiotic because he was also having gastrointestinal issues. Around the same time, I also started him on a vitamin by Kirkman Labs called Spectrum complete. We also began a fish oil supplement. Luckily, my son started talking shortly after we started this and I can't really say what worked best. It may just be coincidence.
My son continues to have difficulty falling asleep, and his pediatrician recommended melatonin. We only give him that when he is really having trouble falling asleep, but it seems to work well. I would give it more often, but I worry about it becoming habit-forming. We only use it a couple times/week.
Good luck!