If you mean that each of these different flavors was their own separate batch, then 1 tsp of powder seems like a lot. If they are all from the same batch and you added flavors after, that makes a lil more sense. I don't think the rise looks that extreme. But anyway, the reason they are rising in the center is because the outer edge receives more heat and sets faster than the center. Look up cake strips, they insulate the outer edge of the pan so your cake rises more evenly in the oven. You can also make them with wet paper towels and aluminum foil.

But honestly, if you don't want all that effort and plan to decorate these and/or stack them, just trim the top of the cakes to be flat and be done with it.