For me, Flex Monthly doesn’t necessarily provide enough water because it is based on historical data, not on current data. I would set everything to Flex Monthly and then take one zone and set it up for Flex Daily. If you post your settings for that zone on the community, and then even post what you are seeing in the moisture level details, the community can help you get it dialed and help you to understand how Flex Daily works.
Also, do you have any empty zones on your controller? If you do, you could set up the empty zone like one of your real zones, put it into a test schedule, and then monitor that to see what it would do. (I’ve done that several times to test things out.)
Are you garden zones by any chance drip emitters? If so, you probably need to play with the nozzle inches per hour to get it right instead of using the default for drip emitters. See Drip Emitter Calculator for Precipitation Rate & Area