It could be a range of things,
You should fill out the trouble shooting forum.


I probly aint right on this, But correct me if I'm wrong,
It could be a nitrogen defficentcy wich is causing the leafs to brown.

What's the ph of your water?
The lights your using?
Watering schedual?
Humidity?
Do you have the right ventalation?

My leafs were starting to get thin and curl inward, But thats cause she was starting to get root bound. So it could be that, Im about just as far as you in flowering, And I had to use 18 gallon buckets for her. =/.