Dual HHO Generator Confusion (Hydrogen Generator)

Ok so I'm a little confused and frustrated by the way my cells are behaving. Basically I have two cells with 4 SS 2.5oz cups and have 1/4" threaded rod going through them in a +-+- config per cell. And I tried each cell by iteself and it only puts out 1/2 liter per minute at 15 amps 12v. I tried two of them in series and got about 800ml per minute at about 25 amps. Then I tried two of them in parallel and got maybe 300ml in a minute drawing 6v 15 amps per cell (15 @ 12v total). I tested the cells, before I put them in and after. And one appeared to have been shorting out, then when i took it out of the water it wasn't? What in the WORLD is going on here? And why am I getting such crappy output? Several people are running multiple cells and getting great output. Thanks and PLEASE comment!