Okay, your temperature swings are pretty extreme.
I will say that in your case, going to a 24 on- 0 off light cycle and running a small fan in the tent for circulation will help you stabilize your temps. That's my primary reason for recommending 24/0 to people.
The soil moisture makes sense; better-rooted plants will use moisture at a steadier rate.
Stones in the bottom are only so helpful; instead, if you feel you've got moisture-retention issues, drill holes in the SIDES of the pots as well to help aerate the soil and dry it out. Use a 1/2" paddle bit.
Give them a light mist with the epsom salts at 1/4-1/2 tsp/gallon and try not to get any excess in the soil.