I have had burn (really potassium deficiency) on a few grows, even my current one. The good news is it attacks leaves, and really will not affect your bud overall. Taste & potency was fine
Granted a healthy plant would be better vs one with deficiencies. But I have had some great smoke from plants that looked much worse that yours.
However as said above, a good flush prior to harvest helps. You should flush the soil which will help get whatever caused it out.
I prefer to flush soil regardless, while you cant not "flush" nutrients from the plant once absorbed from the soil, you can eliminate whats built up in the soil to prevent the plant from feeding off it the last week - or two...
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