DISCOUNT COLLECTIO N BLACK FRIDAY

I was having this same issue for a new customer discount code and them stacking on top of a sale I was having with the prices discounted (strike through price). I figured out an easy way so i don't constantly have to edit the eligible collection for the new customer discount.

I added an eligible collection for the discount code. On the collection for the discount CONDITION TYPE--> COMPARE AT PRICE --> IS EMPTY

This will make any marked down products ineligible for the discount code.