Callaway Irons - Shaft Flex advice

I recently purchased some Callaway Apex CF 16 Irons on ebay, 4-AW for $850. Hoping they're authentic.

My question is, should I have bought them with the regular flex shaft or a stiff flex shaft? I was at a Golfsmith today and trying drivers. My swing speed was around mid 80s and a few low 90s. The fitter told me that I should have a stiff shaft for my driver but didn't really say anything about my irons.

Do you guys think I should return these irons and get stiff shafts instead? Thanks!