Yellowing...

http://img199.imageshack.us/img199/3167/166ra.jpg

The plants have been flowering for around 10 days...the lower leaves are getting yellow...is this normal? What's happening...

Have a read of my comments here https://www.rollitup.org/marijuana-plant-problems/257851-necrotic-spots-yellowing-lower-leaves.html I think the issue is the same.

Look like they need some Nitrogen...
Whats the PH of the water u put in and what PH does it come out of the pot at?

Well I will feed them in couple of days....i wouldn't want to over do it. Last time I fed them, the leaves were starting to show spots and tips were a bit burned..i probably gave them too much..so i decided to delay feeding a bit...I'll try with 1/3 of a proscribed dosage....last time I gave them 1/2 and still it was too much...