A useful comparison
Run a healthy zone, then the weak one. If only one station is weak, look at that valve, a crushed lateral, or heads added onto an old circuit. If every station is weak, look at the supply shutoff, a clogged filter, or the pressure regulator on the backflow.
Clay and added heads
Houston clay does not forgive a lateral that was kinked when a bed was rebuilt. Extra heads installed so a new patio would get water often drop the rest of the zone below what the nozzles need. Call 346-642-6161 and say whether one station or the whole system is weak.