Help !!! J can`t get rid of peak around 5 k

Hi !! Sorry about my english first :( I have a strange problem. When I listen to my monitors they have nasty peak in the upper midrange. When I listen/measure thru only one of them they seem fine, the problem is noticeable/measurable only when they are both on. I have a pair of alesis m1 active. They are standing on a shelf verry close to the wall. My walls are covered with a soft carpet so it should absorb high frequencies. I don`t konow what is happening. Help me please I can`t mix in my control room !!!