Discolored leaf margins on lime basil

Is anyone familiar with this problem with their basil? It seems more prevalent amongst my lime & French basils than my others. It's always on the 'older' leaves, as opposed to the new growth. There don't appear to be any bugs on them & nothing else I would think of as a symptom. It reminds me of the thrips damage on my parsley & dill, except that there is no fecal matter. Both the top & bottomsides of the leaf are clean. These plants were started from seed and have always been grown indoors. They seem very healthy otherwise.

Since this is at risk of going to the next page without reply, I'll take a wild stab to bump it up and suggest- do you use a fertilizer with micronutrients? It doesn't sound like insects and looks different than any usual problems like overwatering or dry air

I think, through diagnosing a problem with my jasmine, we've come to the conclusion that's probably what is going on with all my plants. I'm guessing magnesium, but micronutrients anyway.
Thank you for replying-it's good to get an opinion specifically on the basil! It helps confirm my suspicions.