i have some thoughts. I think that water spilled on your leaf and the light burned it. Some suggestions for you would be to get some plastic saucers and put under your plants so that you can water more thoroughly. You need the whole pot watered. It will make the roots go searching.. Then let the plant drink up any excess in 20 min. If there is standing water, dump it. Then go ahead with the wet/dry cycle.
Also, i hope you have a fan blowing across your canopy as well. One more thing, is get those small ones up on something, I use overturned cooking pots. You want an even canopy.
I do not believe that is from the light. I agree with Rosebud--I think it looks like something was spilled on the leaves and this is what caused the spotting/discoloration of the leaves. Ditto the watering. It does not look as though you have drip trays under the smart pots? You will want to water until runoff and then give the plant a bit of time to wick the run off back up to the plant. I find a use a myriad of other things to get the plants to an even canopy--cardboard boxes, coffee "cans", other pots and containers...whatever you can think of that is the right height will probably work.
Watering until runoff is not flooding the pot. It is getting the entire medium wet so that it encourages the growth of a deeper healthier root system. After a bit of time, any runoff not reabsorbed by the plant should be discarded.
Flooding or flushing and watering thoroughly are 2 separate things. Flooding/flushing involves putting 3-4 times the volume of the bag through the medium and the purpose is to wash out nutrients and residual salts. When doing this, you do not let the water be wicked back up, but dispose of it. But we were talking about a good watering to make sure the entire medium is wet....quite a different thing.