Be careful , if you don’t allow time for it to be corrected it will just spread up to the next set of leaves.
I flushed it about 3 time the amount of water per soil and it got back to normal leaf growing nice and healthy …so she’s back to her normal nutrient feed.
Make sure give a week to see if it don’t spread , than trim or prune.
Ok thanks for the tip …I’m a first time grower 
There are two classes of nutrients; mobile and immobile. Mobile nutrients are nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and zinc (Zn). All other nutrients are immobile. What this means is if you had a nitrogen deficiency (which is a mobile nutrient) the plant would “mobilize” the nitrogen From the lower portion of the plant and move it to the new growth; the top of the plant. If you had an issue with a mobile nutrient, be it a deficiency or a nutrient lock out and then trimmed off some leaves, the plant will just start taking from the remaining leaves, crippling future growth.
The flush was the right thing to do, but what is her “normal nutrient feed”? What’s the EC or PPM of the nutrient solution? Did she develop this problem during a “normal nutrient feed”?