I have a Caretaker system and it's working fine... except for one zone (2 heads). When it cycles around, it gets to that zone and the heads don't do anything and the pressure on my filter rises. I got in the pool and tried to lift them up by hand and they would lift, but no water coming out. When I let go, they go right back down. Once it cycles past that zone, the other zones work fine. How do I know if it's something in the heads or something at the distribution (actuator- 5 port) valve?