Lowryder Flowering Problems

My two little lowryder girls are in there second week of flowering under my 400 watt HPS, Light is 18 inches away from the tops of the plants, they are growing fine, but I have noticed Yellow Streaks down the middle of a few of the leaves!


I have picture attached.

Please let me know whats going on with my girls.

Medium: Soil
Type: Lowryder
Height: 12"
Planted: OCT 1st 2008

These two girls grew to about 8" and then started flowering, This is an auto flowering type.

They were grown under Flourocents until they started budding at 18/6, They were looking very healthy and growing, I put them under the HPS with a 12/12 and now they arn't looking so hott......

Thanks

leave in vegg lowryder is a auto flowering strain switch back to 18/6 or 24/7 or what have you... as far as the yellowing check this out Cannabis Plant and Pest Problem Solver - Pictorial - 420 Magazine hope it helps gl with ur grow

I think it is heat stress, thanks for that last post, Light will be going up a few inches higher, and ventilation will be increased