Help! Dark brown spots on leaves!

My plants are about 3 weeks old. I transplanted them from soil to soilless about a week ago because I was getting overwatering problems. I have not added any nutes yet (the promix bag says wait 2-3 weeks). I watered them with water containing chlorine yesterday and also sprayed the leaves a little bit.

Does anyone know what the problem could be? Is it the chlorine or something more serious?

looks like a scar not a disease or nute problem

I also used Organics Seaplex for foliar feeding a few days ago. Do you think this or the chlorine could have caused the scar?

It shouldn't have, but if you are worried about the cholrine filter then boil the water you are using to water it. That takes out most of the impurities in the water. Good luck