What is wrong with these leafs?

[LoveGrowingIt]

@Kbdwc - I'm having trouble sorting the problems, and there are several of them.

High heat can cause the leaf curling. So can low humidity. They often occur at the same time.

It looks like some of the plants have been watered too frequently.

I also see signs of magnesium deficiency, or possibly light stress.

More information would be helpful...
How many plants do you have?
Are they all in the same place?
What light are you using?
What growing medium are you using?
What is the temperature? The humidity?

My apologies if some of these have already been discussed.

 

[Stokes]

Everything that is in your water that you put into the humidifier goes back into your environment in some form or another. Its why people with hard water get their prefilter clogged up with calcium

Im shooting from the hip here and am not the brightest, but i would say that you gave your plants an inadvertent foliar spray in the middle of the day. Would consider spraying them off just before lights out