AsNoriuanswered grow question 2 years ago All plant is healthy not overfed colour, so excess of nutes not the answer.
Heat could be.
Could be rout bound , too small pot for that girl, first signs
Could be ph issues, they always come up in 3rd week of flower.
Could be just eating hereself, aka a bit too hungry.
That leave curl could be to low humidity for high temperature, check vpd charts in weed grows. Very useful