Bread Shelf-Life and Proving

Toast

My baked burger buns lasts less than 5 days. I use mold inhibitor, 4% of flour weight. I have been seeking answers why this happens. Correct me if I  am wrong. Breads with mold inhibitors last for about 5 to 7 days. Also, does lessening the required amount of shortening will effect in the growth of molds and in proving the dough before baking? What are the causes for molds to grow fast? Advice is very much needed. Thanks

What's in it and where can you buy it?  I've heard of dough improvers such as lecihin and ascorbic acid, but not inhibitor.  I live 10 minutes from the ocean and things can mold fairly quickly year-round.  Thanks!