i have found i have the same problem.
i found that maybe 3% of 1- 1 1/2 TBLs of hydrogen peroxide per gallon of water. and maybe straight vinegar from a spray bottle on the soil or soil less.
i used well water that had been sitting out for a couple of days. and i suppose the molasses helped when added at the time of watering. it, the problem sprang up in 24 hours. i am also using DEMAND CS as a pesticide. hydrogen peroxide will kill pesticides.
i have mixed 1 TBLs of hydrogen peroxide a spray bottle and wet the top of my soil less. if that does not work, i will use straight vinegar.
12/12 started last night.
H2O2 will put oxygen to the roots. vinegar will help my sorta high pH prob.
some have said baking soda on the top of the soil but i don't wanna use baking soda .. like i said the pH deal.
yes i have ran into every problem i could, but i find solutions. this is my first indoor grow. even tho i find solutions i believe it does NOT help my plants with all the stress.