This is a recent development, I use deer park bottled water., freshly opened everytime, to water them with, I just started adding mg at 1/4 strength and I used to mist them which may also contribute.
Do you use coco? Looks like it what's the ph of the water coco is also a calmag leach looks lime a calcium def don't foilar spray I burnt mine doing that
im using jiffy seed starter, i just bought a ferry morse electronic meter, and it's reading the ph to be between 6 and 7 closer to 7. and for the fert analysis every thing was saying 'too little'