anyone know what this is? ( Micro Grow)

Lower leaves are turning yellow, from the inside out if that makes any sense ( starts from the beginning of the leaf) and are dying away.

I think it may be a lack of N. but Who knows. Need some suggestions. Here are my specs.

-200 W CFL
-Soiless Medium
-Fox Farm Trio
-Started doing 12/12 around day 30. now day 39.
-I ph my water down to around 6.0 w/ white vinegar (any other suggestions beside's buying ph down.) because my tap water is to high.
-My temps are fine. 70-85 F

Link to my Sub ---> https://www.rollitup.org/grow-journals/415541-first-time-grower-veggy-box.html

~ Thanks for looking and all the help. I love this community ~

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It looks like it may be lacking a lil N. What kind of nutes you use?

fox farm: big grow, big bloom, not any tiger bloom yet but will later on.

is it possible that thats from lack of light? some times i see that ruffle look on the bottom of some mother plants. that for me may be a light issue.

very well could be. never thought of that. it is rather crowded in there atm.