This is not iron deficiency for sure though. A seven week veg cycle would have no bearing on any of this
I veg plants for months. In solo cups.
The yellowing here, is either
A , lights out put is too bright or it’s too close
B , a mag deficiency caused by the above

C ,Backed off veg nutes too soon still wants n
you are using sdistilled water, that hasn’t been buffered by cal mag every feed well
There’s your huckleberry.
Iron deficiency is crazy rare.
Your plant is far too healthy otherwise.
Been doing this a long time homie.
This is my 2 cents. Click on my profile of you think I’m full if the dung.
In the pic, messed up iron levels relative nitrogen levels. Starts getting nutty with the way they interact.
The iron deficiency here, causes the plant to put n into over drive seeking to fill the void from the lack of iron. and is now causing the plant to pull n like nuts.
Good luck.
