I checked my bottle for the list of ingredients (which I'm sure you already did ) and it only says 'complexed hydrosulfite salts'. Have you tried going to their website? It might have detailed info on all their products or maybe a way to contact them with a question. Hope you find your answer!
the thing is i done a small water change and added prime and stress zyme both according to instructions no overdose and the small shrimp that was in it died but i did lose alot of shrimp previous as well and now im starting to think it could be to do with any of these 2?