Vitamins at Customs in Zihua

Ive heard they are being sticklers at the airport in Zihua for items brought in from the US. Do you know if they are making us declare the value of opened vitamins that I might need for a two month stay? I happen to bring alot...ie, maybe 6-8 bottles.
Also one or two prescriptions.
How would they be about keto candy bars I cant get in Zihua or some other food items.
Just curious. hard to find receipts for these items but maybe I can.