If you replaced the Male side, and it's still leaking between male and female union......then.....it's the female QD. no?
What brand of QDs do you have? could be something simple like an o-ring in the female, it's not the "poppet" nipple in the female otherwise it would leak when Not connected assuming your lead hose ball valve is open.
As for flow, I suspect some moron sold you an inline filter (that goes between the QD and valve) on the wand, and said inline filter screen element is Actually a combination checkvalve/filter and is impeeding flow of your 1/4" solution line. This is a place for a Filter Only not a checkvalve, a check valve does no good Behind the wand valve where it's constantly under 500+ psi when it is a 7 psi check valve.
Another possiblity, some of these cheap kingston and kingston-tech valves have a small orifice inside the threaded area, if you screw a 1/4" nipple "too far" into one, you will block off the already small orifice by 1/2 or worse, so pull the nipple and inspect to see if it looks like it's seating too deeply. a tapered pipe thread does not need to, and should not be maxxed out in a fitting, if you can't see some "thread" when it's fully snug, it's a bad sign you are bottoming out inside the fitting.
