Seams that you have decreased Nitrogen too early.
850 ppm is ok , but not if you Feed with each watering every day.
Your plant is suffering from N deficiency and P-K over fertilizing.
At this stage the roots don't absorb N anymore, they only intake P-K.
You shall give it a good flush cuz you might have nootz build up, and hope she has stocked enough N to finish properly the top.
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