My red velvet cupcakes keep sinking in the center! I can't figure out why. When I pull them out they deflate and sink or puff up then deflate while they are still baking. I think my oven may run hot?. I've already thrown out 2 batches tonight that I tried using self-rising flour for but that seemed to make the problem worse. Recipe says 325, been baking them at 400 for 2-3 minutes then turning temp down to 350. I tried reading up online about it and it seemed like raising then lowering the oven temp might help so I tried that and it helped for a few batches but now they are sinking again. Baking powder and baking soda are not expired, but I also wonder if I am adding too much? Recipe calls for 1 teaspoon of each. Tried filling cups less and it sort of helped but those were coming out flat. I want nice domed tops :( I have other recipes that come out great so I am not sure why this is happening.

I read in Bakewise some recipes that don't have enough flour and too much fat can do this, so I am thinking of increasing the flour and adding an egg like she does in the book, but she said it does change the taste, and the fattier less structured cakes are more delicious. But I have 2 orders for these cupcakes coming up and they've sampled the recipe I'm currently using and that's what they are expecting so I can't really change the taste too much. I wonder if the cup of oil is too much and I should reduce it a bit and/or add more flour?

The recipe I am using is:

2 C flour

2 C sugar

1 T cocoa powder

1 t baking powder

1 t baking soda

1/2 t salt

1 t vinegar

1 C oil

red food dye

1 C buttermilk

Cross posted on the cake disaster board as well..thanks in advance for the help!!!