every leaf that's green and healthy is adding to the overall photosynthetic output of the plant, so any leaf that's green and healthy should be left on the plant . . . unless you're pruning low, unproductive nodes low on the plant (lollipopping)
a leaf at the second or third node on the mainstem is one of the oldest on the plant . . . and it's productivity is waning . . . this sounds like a product of age, and it's probably of no consequence whatsoever to the overall health of the plant . . . it's normal - clip it off
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