Morning Glory Wilting

So, I went out into my garden this afternoon to check on my beloved plants; who have been growing so healthily since I planted them and my morning glories look really sick.

They looked kind of like this yesterday too, and I thought it was because my nephews watered them and they got a bit too much water, but they looked fine again last night.

I suspect it may be due to the heat since it was super hot - my feet burned on the decking, but I'm not really sure and I would like to know if this is due to heat or overwatering, and possibly how you can tell?

Honestly, this is one of the first plants I've grown and to see it come this far and then get sick is heartbreaking

 

Hey Shiney, thanks for the input.

I did give them a good water earlier, the sun has made it's round now and they're back in the shade and now they have gone back to their usual appearance again. It does make sense that they are lacking water rather than too much sun, they are a plant from North and Central USA after all.