Amazon diaper code users ?

TinyPinkBug

I have used codes in the past but not in a couple months.  I was just trying to buy diapers, and it is automatically taking am extra 20% off ( +30% ) without entering a code.  I try to enter a 20% code but it says it has already been used ( I tried several codes).  I also tried a $10 off code and it says not valid on this item.  I bought one pack with the 50% off, then tried another pack of different diapers and it applied the same 50% discount.  Is this happening with anyone else's account?