Marijuana leaves turning yellow, advice?

A question from a fellow grower:

Can you please explain why my SSH plants the first leaves are turning yellow but all else looks OK
The plants have only been feed pH 6.0 water and no food,seedlings are 10 days old
I am using a 300 W led lamp and growing in soil
I will use marijuana Booster food for this grow
I raised the lamp as my initial thoughts were light bleaching
I have attached photo for your consideration.
Look forward to your advice

Light bleaching, if it is that, it will happen worst at the top, the part that is closest to the light.

What is the pH in the soil, at the root zone? This probably shouldn’t be a problem with you already pH’ing the water, but it could be.

What is it growing in? It could also be it is time to start adding a little nutrients, that is a small container, and the plant does have some true or full leaves, so it should be able to start using some nutrients, maybe.

I’m also a little concerned about maybe an over watering situation. The leaves do look slightly bloated, but it is hard to say with such a small plant. But maybe, and over watering can cause a magnesium deficiency, and lower leaves turning yellow can sometimes indicate a magnesium deficiency.