Um, what is that leaf fragment from?

And what does the rest of the plant look like?

This is the tomato pests and diseases forum ;)

The rest of the plant seems healthy. Good stems and branches. The issue seems to generate from the outer edges and moves in with small spots growing on the inside. The spots also show a trend of appearing closer to the edges.

Yes, I know this is the tomato pests forum. But that doesn't guarantee that people ask only about tomatoes.

If it is truly as healthy as you say, why are you concerned about one very small piece of one leaflet?

You've removed it. Thus the problem -- if it is/was -- is gone.

Please post a picture of the entire plant.

I forgot to mention this is happening on MOST of the leaves on most of the plants.

Ran short of water. Now you must figure out why.

Some ideas:
potting mix to dry
potting mix too wet
temperatures very high.
high soluble salts as in excess fertilizer and/or no drain hole or stingy on the water and it never runs out of the drain hole.

More reasons --your turn to list a few based on what you know.

The soil I bought at Walmart. In hindsight, this may not have been a good idea. it was thoroughly wet (not soaking) during planting. Growth was amazing. I did not keep it at the same hydration levels, so iff anything it could have been too dry. My test was to put my finger in the soil. First 1/4"-1/2" is usually dry or lightly wet, then the soil underneath would be damp.

Growing inside in an air-conditioned environment at ~70+ F. Fertilize about once a week with a focus on Phosphorous.

I think I found the issue. http://imgur.com/o8sttN6,3XsYM9c

Good job with the research!

exact same thing is happening to me ,, except im not over watering