Looks like a type of leaf miner - fly larvae that burrow inside the leaves.

Paulie, put a squirt of dishwashing liquid in your water when you water. It acts as a surfactant that makes the water "stick" to the soil, so it doesn't just run out the bottom.

I've experienced those leafminers personally, & that

really looks like it. Try examining the blackened areas to see if they are hollowed out between the upper & lower surfaces of the leaves.

Unfortunately, nothing you can spray will kill the miner larvae, since they are protected inside the leaf membranes. I remove affected parts & try to squish the larvae inside the leaves w/ my fingers. The damage looks minimal right now as well.

I looked inside the leaves but I dont see anything. The leaves do separate very easily if there were like two pieces, top and bottom.

Then I'd say it's leafminers - larvae may've pupated already.