Leaf

Considering that it is an outside grow you might want to inspect for insects on the underside of the leaf and or along the stem, that being said it is only on a single leaf. It could be early signs of a deficiency or toxicity, I would personally leave the leaf if there were no signs of insects so you can monitor how it changes. If the leaf stays the same then it could be light burn from water accumulating and acting like a magnifying glass in the heat. However, if the leaf continues to degrade and change colors you could use that as an indicator of what might be wrong. You could attempt to flush with a half or quarter strength nutrient if you are using any, and or PH adjusted water to possibly break up any salt accumulation you may have in your soil. Hope this helps.

Pull it off.. problem solved.. if it’s only on one lower leaf I wouldn’t worry about it, it’s outdoor the leave’s are going to be eaten at some point but your plants are big enough to handle it now. Only when they’re seedlings you need to worry about it as much

its outdoors so shits gonna happen dont worry about it too much as long as they look and grow fine. also keep an eye out for bugs outdoors do your ipm.

Take a good look overall if you find any bugs , if don't then it may come from your nutrients. Be sure to use calmag, when feeding don't let the nutes touch your leaves. Good luck

Water spots from spilling fertilizer on the leaves.

This looks like you might have some sort of insect that's starting to munch on your plant... check the underside to see if you can see anything - eggs, etc... This has nothing to do with nutrients. Good luck!