Can supplements like tumeric, black raspberry, mangosteen, pomegranate & noni aggravate existing acid reflux?

Yes : Turmeric is often touted as one of the best natural remedies for reflux but can aggravate reflux for some. While not common, it is likely some of the others you mention might cause reflux in some as well. The best way to find out is to stop all of them and restart one at a time to see how you react. This is an interesting site: http://earthclinic.Com/cures/acid_reflux.Html.