Circulation issue. Based on what I think I see I have an idea what part of the issue may be. Looking at the suction side you have three valves, A, B, and C. The first valve to the left, appears to control whether you are pulling from the spa or the pool. The next two valves, B and C, I am guessing look like they are controlling how much is to be pulled from the skimmer, and/or how much is to be pulled through the floor drain. Since code requires at least two floor drains, that is why I am assuming the valve to the right controls how much is being pulled from the floor. That valve on the right is almost closed. Therefore, if I’m correct, you are pullin, almost exclusively, through the skimmer!