if your plants are over watered and drainage is poor then add some peroxide to to help oxygenate it helps a bunch... i do a couple of tbl spoons per gallon.
I have done this, I was warned by someone not to do this in organic soil though, because you may kill off some of the beneficial bacteria. I have used a 3% hydrogen peroxide solution (just to clarify, NOT peroxide like you put in hair, I've seen someone make that mistake before) to achieve this, but I have had some pH issues recently, and that might have had something to do with it. I doubt it, but you never know.