small problem getting bigger...

Hi,
I m growing 3 girls (2 blue mystic and 1 white rhino, all from Nirvana) in a small grow box under a 400 HPS. My plants are 6 weeks old (5 of veg and just getting out of their first week of flowering.

The problem started 3 weeks ago. The lower fan leaves started to turn yellow after I raised the concentration of my nute. I flushed them with water with a PH of 6. It stopped for a couple of days but the leaves started turning yellow again after a few days.
I believed that maybe it was a N problem so I decided to give a them a small dose of nute (a different one). It didn t help and now the yellow leaves are spreading to all the plants and the rest are pale green...

The temp of my room is 28 - 29 C (82-84 F).
Help please, i don t know what to do.

Just out of curiosity have you checked your runoff Ph?

And what soil are you using...... if youre using roots organic Ive had this happen with this soil.

Before adding anything more to your soil I would check the simple but most important things first. By adding more to the soil you could be compounding your problem. Always check the Ph of your runoff before adding things. You would be surprised that Ph is usually the number one problem most people overlook.

^Agreed, it's likely a PH problem, with your PH being too low, locking out nitrogen, or making it's availability limited. Next time you flush, use something PH in the 6.5 range, even a little higher, because it'll keep your soil PH higher, longer.(I use 6.6-6.8 for everything I give mine) Starting at 6.0, is at the lower end of the spectrum, which would explain why it worked for a little while, then quit, as the PH dropped again. If I were you, I'd flush 'em again, with water PH'ed at around 6.6, until your runoff comes out at 6.6, then give them a feeding of high-N veg fert, at least 1/2 strength. They are in need of some nitrogen, badly.

Thank you all for the imput.
I ve been watering them with a higher ph for the last 2 weeks (6.5), but i ve never checked the ph of the runoff. I ll flush again with a ph of 6.6+ and check the runoff this time.

For ipack... I m using good quality soil from holland that I buy at the flower market next to my place... I discovered a shop selling better quality soil not too long ago andwas thinking to give it a try for my next grow.

I flushed again with an appropriate PH this time and the yellowing has stopped and the new leaves are a nice dark green... hope they will stay like that.
Just a quick question. Is it possible for my older yellowish leaves to get back to a nice dark green again? (I guess not, but just asking)
Anyway, thanks again!

No.... yellow leaves will stay yellow. Sorry bud.