I'm just getting started and so far all of my cakes have been white cakes but I've got a couple chocolate ones coming up for some birthdays. I doctor a mix with sour cream and pudding mix usually this time I tried it with the same brand of mix, added the other "doctoring" to it and 3 out of 5 of the chocolate cakes fell in the middle! What should I do to remedy this issue before I need to have the cakes ready? They are only for family but I want to give them the same quality I'd give someone who actually ordered a cake.
Thanx.

Do your cakes sink in the middle after you take them out of the oven?

The cakes might be underbaked. Try adding more time.

the centers are caving during baking. I've coked them extra time - they are done when I take them out (toothpick comes out clean and touch test also confirms) when i level the cakes it seems a bit 'doughy' in the middle but fully cooked.
I usually use sour cream in my white cakes but today I used vanilla yogurt. I'm not sure if it's the yogurt or of it's chocolate cake vs. white cake.
I usually bake at 325 degrees and it generally takes a lot longer - but they have never 'imploded' in the centers before.

What brand? Is it one of the ones affected by the size changes?

I have been using a generic mix all along - still 18.25oz (get it at ALDI's) so I don't think it has anything to do with the size - they just sink in the middle - this is something that never has happened before - but this is the 1st chocolate ones I've made. The white and yellow mixes turn out great.

I think the sour cream or yogurt should be reduced and see if it helps.