I have a eight zone sprinkler system. It is ran off my drilled well. I have a submersible pump. My water pressure switch has a cut in of 40 and a cut off of 60. Recently noticed my rainbird 5004's weren't spraying out as far as normal. Started watching my pressure gauge by my water pressure tank. I noticed that when the system switched from one zone to the next pressure would drop to 23psi and it only comes back up to 30psi. Normally it would stay at 40 or 41 psi. It doesn't seem to matter what zone you start on it drops when going on to the next zone. Also the first zone you start on will read 41psi. My valves are rainbird dv-100's. Any help would be greatly appreciated.