Leaf problem

I have some plants in a greenhouse and here lately the top leaves on some plants have been going very limp and floppy. I water them when their top 2 inch of soil is dry and it gets around 85 to 90 degrees mid day. Heres a link to some photos. https://www.dropbox.com/sc/3g8ulcd62gloco8/AAAhlYKDqmbPyeZyqH42bKH9a thanks in advance.

Looks like normal heat stress. Do they perk up in the evening when it cools off? If they do then I would not worry about it. If not, then it could be a sign that they are thirsty, but that is doubtful considering how you are watering them. I would suggest that you make sure your soil is dry a little deeper than 2 inches before watering. With those temps, it could dry out quickly on the top and be soaked on the bottom half. Maybe try putting a layer of mulch on the top and be sure that your soil needs water before you give it a drink.

Some do perk up but i have a one plant thats top leaves stay limp. I will start watching how i water them more.