See I grew in soil for years and years and you always hear of people saying its this magic "Buffer", yes its more forgiving than Hydro but it will not buffer water outside of 5.8 - 8.2 in my opinion. anything outside this range and after a week or so you will see issues.
Those plants looked nuked, I would just water with plain water straight out of the tap for 2 - 4 days maybe more. If your using a branded soil made for Cannabis growing you don't need to add any nutrients either.
If your water is hard or very hard try not to add any Cal/Mag unless its really needed. Calcium is added to tap water at the water treatment companies in quite high doses to make tap water better for our bones etc, so unless you do have a serious PH problem there should never be a need to add it to water, and when you add a load into tap water and give it to young plants it overcook's them. I've had a bottle of Equilibrium Cal/Mag for the past 18 months or so and used it once.
Leave some tap water out over night and water them with that for a few days and I rekon they'll bounce back. Less is more.
Best of luck.
GV.