See, thrips are good! Your almost there. Aphids outright suck. Mites are in the middle.
That crisp line is your issue. This is an easy fix to rid yourself of the thrips.
Calcium is a lot more than a nutrient. It's the key piece. It conditions the soil as well as acting as a nutrient. It creates tilth and in conjunction with Mg, is the main player in your CEC. So if it's low, lockout and PH issues are occurring. She needs Calmag.
Use an organic one if possible, or buy some prilled dolomite and make your own.
Low dose calmag used a couple times is far superior to one big dose. Calcium works on contact to fix the soil, and in 2 or 3 days it's into the plant fully. Once the line gets fuzzy then lay off the calmag.
Try one dose as per light feeding instructions on the container, wait 48 hours, then brix her agsin and follow the refractometer results. You want fairly fuzzy.
@g-one-three has dialed in photographing refractometer results. G, you got some examples for Lady C of good and bad here?
Then monitor weekly and when the line is almost crisp again, you give her some more calmag.
When that line goes crisp you are about 2 weeks away from the classic brown-spots-on-the-leaves calcium deficiency, which means she is stressing for 2 weeks before you hear about it. Starving for cations too, and nitrogen gets locked by magnesium when Ca gets low, so you are in the beginnings of a big crash. Full starvation.
Calmag her today and in 2 days your golden again.
If you get clawed leaves, which are indicitive of nitro toxicity, thats calcium releasing all the locked up nitrogen at once. You want that to occur before flipping to flower, where a nitro bomb can really hurt.