@okotlicki, thanks for reaching out. As you know, flex schedules water on an as-needed basis as they have the Fixed watering time intelligence features, Water Budgeting (WB) and Weather Intelligence (WI) built into them. I believe the issue you were experiencing with your Flex schedule is rooted in a display bug that we are currently working on. For more information, please reference this community post: http://community.rachio.com/t/hot-days-ahead-and-flex-watering-less/1980/6
In short, the issue you're experiencing is that the forecasted schedule is overriding the observed schedule on the moisture graph. This isn't a problem as long as the weather forecasts and weather observations line up, but when these differ, the graph might show tomorrow's watering schedule today. We are working on a fix for this issue, however until then, there could be a display issue with Flex Schedules.
When in doubt, please refer to your activity feed as that will always be the record of what did and didn't run on your Flex Schedule.
Circling back to Zone 3, it didn't water today as it's Allowed Depletion didn't reach the threshold setup (30%). The the moment, Zone 3 still has 9% of it's available moisture balance available.
It's important to remember that your zone's moisture balance does not equal the allowed depletion. They are different percentages. In your case, for Zone 3, you have Allowed Depletion setup at 30%, meaning the system will water once you've used up 30 units out of 100 available. Keep in mind that at 30% allowed depletion, the zone still has a 70% reserve available. The zone is far from being out of water and pushing out the next watering a day encourages the plant to grow deeper roots to pull water from the soil reservoir that is the 70% reserve.
At this time, Zone 3 is forecasted to water tomorrow. Should weather conditions change to warrant extending the schedule, Flex Schedules will do this automatically roughly one hour before your scheduled watering time after pulling and reviewing the most recent weather data.
As @katerri22 put it best, Flex Schedules are designed to only water when needed. If micro-managing the system is your preference, I would recommend you switch to a Fixed schedule.
For more information on Fixed and Flex schedules, please refer to this support article.
Hope this helps. Let us know if you have any questions or concerns.