Yellowing in middle: auto in soil

[Cwmoore577]

I have an auto in early flowering that’s starting to yellow mostly on the fan leaves in the middle of plant.

It’s a strawberry cheesecake from seedsman. It’s in Fox Farm Strawberry Fields soil.
It’s 6 weeks from sprout.
Lights are a 100w output blurple led and a SunSystem HPS 150.
It’s been watered every 4-5 days with mostly RO, a couple times tap water (150ppm).

Last watering (Dec. 7th) I gave it RO water with a low dose of CalMag and BioThrive Bloom (2-4-4) at 320ppm and pH of 6.8.

 

[Chris Scorpio]

I'm Cornfused

You have fed it before, or you just did feed it for the 1st time

 

[Cwmoore577]

I'm Cornfused

You have fed it before, or you just did feed it for the 1st time

Other than the calmag I put in the ro water, I gave a small dose of biothrive grow(4-3-3) on nov26th and then the bloom on dec 7th.
Had no issues or signs of it being hungry until now, the soil kept it fed.

I’m thinking maybe nitrogen?