Leaves curling up and dying.

I agree with Mosherd7 i had exactly that problem in my summer grow and was definitely heat stress. Check out your temps range, you're probably around or over 30 celsius. Try to lower it somehow, increase air movement on the plant or cool down the room. Sometimes, like my summer grow where outside temps were insane, there is not much I could do then. Now is a far more easy season to solve this issue.

flush with clear water and left her for 3 days... is it soil?

Looks like heat/light stress to me. Check the temp of the tent, if its higher than 30, do something. If not, move the light further away from your plants.