thanks for the help weedhound.. sorry i havn't posted up pics it has been crazy around here . (3 kids and christmas.. what a combo!!) i have sorted out the problem ph is stable and the plants are looking great! :thumbsup:.. what i did is run a flush of ph,ed water h202 and calmax for 2 days the plants stared to look better after a couple of hours but on the 2nd day started to look a bit yellow. i then dumped the res and filled it with 1/2 strength nutes calmax and h202 and now they are looking better than ever... wohoo . the thing that has me stuffed though is this fixed the problem but what might have been causing it in the first place?