Why are my red velvet cupcakes sinking...I use the Duncan Hines red velvet mix...I use milk instead of water.. Any ideas?

AWere they underbaked? Did you check the expiration date on the box? The baking powder and or soda may have expired.

Thanks for relying. No I didn't check the box..for expiration date...Total waste.
 

AYou need to not open the oven until they are completely done

Thank you.  Some one else posted a reply sugguested I may have underbaked..at first I thought no, until I broke one open and it was a little wet in the center.  Funny thing though, I inserted a tooth pick in the center and it came out dry...I will try again..As far as opening the oven door, I did open prior to finishing baking to check on them...I will put all this info together for the next red velvet cupcake experience.