Extreme plant problem!!!!! HElp

[BackWoodDrifter]

I took a new pic with a diff. resolution

Nope pilgrem not workin how are yu uploadin them? with this site tools i be hopin

BWD

BackWoodDrifter Reviewed by BackWoodDrifter on 01-28-2011. Extreme plant problem!!!!! HElp :( In the period of 12 hours , 2 of my plants have lost all upper stem vigor. the small one was looking good the day before. the tallest two are 8 weeks in veg and the small one is about 6 weeks. The bushy plnt seems to be ok but the upper leaves are pale yellow. I have kept the ph around 6 , this is only my second grow so im still new to this. any advice at all is appreciated. Rating: 5