Magnesium Deficiency?

This is my first grow so i'm probably seeing problems where none exist but i'm looking for some advice. This plants are about a month old and the leaves have recently started to lighten around the edges. I'm concerned about magnesium deficiency.

My tap water comes from a groundwater well. The pH is neutral at 7, i haven't tested my ppm but i'm guessing that the water is reasonably hard based on the scaly residue left behind when tapwater evaporates. I pH water and nute solution down to 6 when i water. Run off is tough to test with an aquarium tester but it seems a lighter shade of green than the tapwater so i'm thinkig it's between 6.5 and 7. I have a cheapo Rapitest pH meter that also confirms this as it reads just under 7.

Here's some pics of the problem babies:



Any advice or thoughts are welcome.

Earth Juice would probably deal with that.

I had the same deficiency early in my grow, from a combination of lockout due to pH and a lack of Mg in the nutrients I was using. The lower leaves of my plant were the same colour. Zinc deficiency looks quite similar if I remember right.

I'd be looking at the label on your nutrients to find out what's actually in it. Then I'd be looking at using another feed if there's a lack of something. The Americans on here talk about "Cal-Mag" for calcium and magnesium deficiencies. I can't find the same product in this country but I have a lot of different nutrient solutions to play with.

Good luck.