What percent protein is their current mash?
A drop in protein could slow egg production some in theory.
A change in feed could initially cause a drop in production, just because some chickens are picky and sensitive to changes in diet.
Also, the switch from mash to pellets could initially cause a drop in production, again, just chickens being picky/sensitive.
Also, 14% is lower than any laying pellets I have ever seen available... so I question if that is a high enough percentage of protein for actively laying hens... I don't off the top of my head remember what is recommended.