Plant leaves are turning light green from the top down with purple striped stems

For the life of me can’t figure out what is going on with this autoflower. The plant about 7 days ago was mostly fine. Over the past few days it’s been slowly turning light green/yellow from the top down.

I’m running a 200w QB, and thought maybe it was too close. I bumped it up about 2 days ago and nothing has changed. The issue is not progressing very fast from what I can tell comparing photos from a couple days ago to today.

Info:
-Plant is 46 days old (auto)
-Fox Farms Ocean Forrest w/ perlite and dolomite lime
-Tent is at 79f and 52% RH on average
-2 days ago it got water, and only water ph’d to 6.45 with a 150ppm - 25% runoff @ 6.8ph / 105ppm
-Before the most recent watering it was fed 700ppm with Fox Farms Big Bloom and Tiger Bloom with added CalMag and unsulfered molasses
-200w QB

I took a straw and poked it down into the soil in a few places and used the captured soil to do a slurry test with litmus paper and I was getting 6.5-6.8 from what I could tell by matching the colors of the litmus paper. My ph pen showed 7.2, but I suspect it was off by ~.4 because I calibrated it the next day and it was off by a few points.

I’m starting to think that since the ppm of the runoff was so low after last water, that maybe it’s showing deficiencies. But I’ve also had another person tell me it could be the early stage of a nutrient toxicity? I just don’t know.

Some of the stems have purple stripes on them and the fan leaf stems are purple only on the top of the stem facing the light. I have read that this was a potential ph issue.

Im really conflicted on what to do. I don’t want to be chasing my tail and in turn cause lasting issues.
 

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