have you tested the accuracy of that?
That is as accurate as a crack whore. Get the chemical tester. A few drops and read the color. Your ph is way off. You've got to rinse and water feed only for a few days. Then corect you issue. What are you using for nutes and soil? True organics you don't have to ph. PHing in organics will cause these problems. And if you haven't figured it out yet, your $15 tool is crap. We spend hundreds and have them mess up from improper maintenance. But what you bought might have been ok for 2 to 4 weeks but was never accurate the way you need.
everything i have was given to me from a friend from lights, fan to soil and the soil was some organic soil mix with a bit of compost my nutes are bio gold liquid plant food 10% nitrogen 4%phosphorus 6% potassium with trace elements dont know if you have heard of it and my plants are from a bag of weed that had seeds in it lol dont know the sex and gonna flower in a few days and yes i know everything ive done is wrong but hey thought ill give it a try i got 20 rooted clones from them so if i fail i can try again
leaves will always show the damage yellow out and fall off look at the new growth
If it's nutrient lock-out - foliage feed this will help the plant up-take nutrients - flush when foliage feeding because you are feeding the plant via the leaves