I should also say I have 3 butternut squash plants and two rows of carrots in the same bed and they're doing great.

need pictures please. the heat could be a factor do not know without pictures.

I just had a similar problem last night, the top most leaves were curling up and very thin feeling, almost like wilted lettuce. I felt the soil and found it be pretty dry, so I watered really well, the leaves today have rolled back out, though the damage was done already I guess.. They're kinda warped/stretched now. Normally the leaves would lay flat if you pressed them, but now the center will bulge up or down while the outside edges lay flat. Hard to describe.

I noticed brown spots today too, and was considering posting and asking about it. They're not very big spots, maybe as big around as a pencil. I'm watching to see what the plant is going to do, I think my brown spots might just be where water droplets magnified the sunlight and burn the leaves.

What the heat did to my beans.

Here is a link that might be useful: DFW Gardener

Mine don't look anything like that. The only brown is just brown spots, the plant itself isn't dead or anything, just the top 3 most (completely formed) leaves rolled up.