rainbird

I have a five-year-old, 4 station system sprinkler, two stations higher than the manifold, one lower and one dripper. Orbit valves, Hunter rotator nozzles, Rainbird controller. When I turn on any station, either manualy or via the controller, the pressure is so low I don't get an adequate spray...

4 zones total on a Rainbird system. 2 zones are perfect and my pressure gauge runs at 40psi. 1 zone is not working and no resistance on the solonoid so pretty obvious there. Lastly, zone 2 is releasing some water but very low pressure at a shaky 20psi and can hardly lift a sprinkler head. Pump...