What happened to my macarons?
I work at a charcuterie but we are partnered with a professional baker who provides us with macarons to sell in our store. From your picture, it looks like the tops of your macarons have deflated.

I wouldn't decrease your temperature, but instead increase it. Our most common problem was deflation and often times our temperature wasn't high enough in the oven. Also, it is of prime importance that you do not take your macarons out until they are done, or they will deflate and never rise again. Make sure they are cooked through before you remove them.

Also, if your ridges are cooking faster than the middle, check the position of your oven. Every oven is different and may have inconsistencies in heat dispersal. My own oven is hotter on the right side, and I have to be careful to rotate things accordingly. I heat macarons, biscuits, and souffles with this in mind.