Water Pressure Drops. No sprinklers

Rachio 16-Zone system professionally installed. About 6 months ago, when the city installed a digital water meter, we began to notice significant drops in pressure every morning between 7-9am. This is especially bad when our sprinklers run (once a week). I just noticed that our sprinklers are not actually running. The Rachio is saying “low flow” and I noted today there isn’t enough pressure to actually activate any of the sprinkler heads. When I turn on any zone I go from 75PSI to > 20PSI. The actual meter at the street shows around 5-6gpm in use which is about what the Rachio says I’m using (the sprinklers tend to draw 12-15gpm when working correctly) and we never saw a noticeable pressure drop before.

What the hell is going on here? Our water bill isn’t crazy high, there isn’t water pouring out of anywhere, the meter doesn’t seem to indicate a leak, there are no wet spots on the lawn or geyser, or anything to signal a leak.