OMRI certs are a good thing, but there are a lot of good 100% organic nutes and amendments out there that don't have the stamp...All Natural, 100% Natural, or 100% Organic listed gear should be all good. If suspicious, read the ingredients....anything that says chilated anything is no good....they will contain chilated salts to help force the plant to uptake the nutes.
The OMRI certs cost a good penny to obtain, so a lot of smaller companies can't afford to get it.
Hope that helps Dude!
Peace