Question Please help Early veg. plants are getting sick

[Stomper1963]

Yesterday I did not see any of these marks on any of the plants all of a sudden these light brown burn marks appear. The only thing I can think of I may have let the soil become to dry and not water enough in fear of over-watering. I know it's very hard to diagnose without much info so here is a short intro. Mostly kept inside my shed with 4 x 22watt LED effective brightness 1000w. Been taking them out to get some direct sunlight when wind is not to strong as the stems and leaves are still a little frail. Using bottled water no nutrients added. Using vegetable Pro soil for the plants in vegetative stage and potting soil for the seedlings. Watering every 2 days but have noticed it may have been dryer than it should be. Any advice is greatly appreciated. Gave them a good watering this morning as soon as I noticed it. Thank you

 

[Colamaker]

It can be a few things. Potassium deficiency, ph fluctuations, calcium deficiency, manganese deficiency.here is a chart of leaf problems. https://www.growweedeasy.com/cannabis-symptoms-pictures

 

[Stomper1963]

It can be a few things. Potassium deficiency, ph fluctuations, calcium deficiency, manganese deficiency.here is a chart of leaf problems. https://www.growweedeasy.com/cannabis-symptoms-pictures

Thank you for your reply. I thought it was Potassium deficiency but I guess my first hunch was correct. I was so worried about over feeding them that I let them get way to dry. Especially the potted ones. So I gave them a real good watering and the next day they were perked back up and flourishing again. Watering properly is not as easy as it seems. For seedlings in my small red cups I read to water more often 2 times a day but not so much just enough to get them little more than damp. The ones in the pot I trying to water once every couple days but enough water to so it can sink down to the roots. Some have suggested to pour until it comes out the bottom holes but not sure about that.
Thank you again, cheers