Hey there - where do you get your water? If you're using regular tap-water then your problem may be a high ppm level in your water. My tap-water ppm is around 350 and is pretty much unusable. The pH is 7.5 but is easy enough to lower with pH-down. If I were you, i'd buy some RO water in the store and pH-down that to about 6.0 and see if your plants like it...if so, you may have a ppm issue, not a pH issue - and that would tell you that your water source is the problem.

Hope that helps! That was what happened to me...