Just looked at my plants and a few leafs look like this eny one no why ore how to prevent it im 2 weeks in to flowering with a 600w hps in 5 white widow big bud and 1 og blue in flood and drain trays and every plant has this on leafs near the bottom of the plant thanks
The little hooks at end of leaf tips up top is probably a sign that she is at or near capacity on the levels of nutes she can take. Not sure I'd worry about that lower leaf unless it is spreading up.