Is this a magnesium deficiency? [pics]

Hey,

2x GHS Trainwreck; 2x GHS Jack Herer
285w of CFLs
5 weeks old
BioBizz All-Mix Soil with additional feed of 3ml of biogrow per litre
Using tap water (left out for 2-3 days) and distilled vinegar for pH down (6.6)

I was absolutely cruising with these plants until recently. I think the yellowing was down to underwatering and thus low nitrogen absorption, but I have fed and watered them 2 days ago and they are still yellowing.

I am more worried about the light green parts on some of my lower and younger leaves - can someone tell me if this is a magnesium deficiency and if so, what I should do? Is all this yellowing gonna affect my bud?

Would really appreciate some experienced growers telling me where I am going wrong. Thanks!

Looks like a nute deficiency. Buy some CaMg+ from General Hydro and add to fertz. You might do a teaspoon of Epsom Salts into a gallon of water and then use that as a foliar spray to confirm you're getting enough Mn as well. They should take about 4 days to respond.

try raising the ph rather than just chucking more food at it....

Hi there. It seems I have the same problem as you do
(https://www.rollitup.org/marijuana-plant-problems/576742-yellowing-leaves-problem-some-advice.html).
We use also the same soil and same nutrient
but I gave them (white queens, white widow and ak47) 2mg of BioGrow instead of 3 that you did.
I am almost sure that this is coming from wrong PH and nutrients beeing locked. I am waiting for
my meter to arrive to confirm it.

I am curious to know your run off PH?
I had a very similar problem where my run off was WAY TOO LOW and it came on all of the sudden.
Ill sub and hope that you can find out the prob. =)

Bquamb

Yes, it looks like a Mag issue. 1 Tbs per gallon of epson salt or use Bonticare Cal- Mag at 5ml per gallon.