I believe sulfur was the 'proprietary' mite deterrent they crowed about so looudly when it first came out...they no longer crow about the mite thing.Is there any way you can return the unused bags of layer feed for credit? It's worth a try.
I have had the experience of having my hens ignore layer feed, and go crazy for Purina Flock Raiser. Chickens have taste preferences. You really do not need layer feed as long as your layers get oyster shell free choice.
I also recommend fermenting your feed. I've had layers that I was certain were past their laying career come back into full regular lay after being on fermented feed. The transformation has been truly stunning.
But, please do not try fermenting Feather Fixer! The stench is absolutely gagging! There's something in that formula that releases a tremendous amount of sulfur gas as it ferments.