Your richdel valves are the "jar top" type correct? As in, to disassemble, you need to unscrew the top. With no pressure in the mainline, try tightening the cap. I don't recall if you had disassembled the valves before. But, it is important that all parts are as clean as possible before reassembly.
When you changed selonoids, was there an o-ring in the solenoid? The new selonoids have one preinstalled, just making sure you didn't remove it when you removed the white plastic keeper.
Only other option is a leak in the fittings, or runoff from sprinkling.