Given no useful information, no one will be able to make a diagnosis.
Here...
http://boards.cannabis.com/plant-pro...anted-one.html

Tell us about your bottled water. Is it drinking water? Is it tonic water? Is it distilled?

Fill out the form. I think you've got a problem with your water source, either pH or sodium levels, and that looks like a soilless mix... again, you NEED to be checking pH on the medium until you are confident that its behaviour is predictable.