Leaf spots

I started getting spots on a couple bottom leaves on my veg. Can anyone tell me if this is a cal-mag issue? Plants were looking great and are about 5 weeks old. Growing in happ frog soil, worm castings, perlite and dolomite lime. Only fed a couple times using Dakine 420 base and grow.

Could water mist on leaves cause this? I did have a seedling near this plant I was misting....

It could be phosphorus deficiencies, but if you just 5 weeks into veg than it most likely is a "watering to frequently" issue! Plants are not very smart, they will keep drinking and drinking, and if they drink to much they can't evaporate off all that excess water and when that happens rot forms in all those areas that are holding excess water, brown and black patches in the leaves and lots of outer edge leaf rotting!