Yes, the temperature definitely could have something to do with it.
When chickens drink large amounts of water (like to cool off in hot weather) their droppings get extra-watery. I don't know for sure about the throwing up, but I think it could also be caused by them drinking much more water than usual.
If they look OK otherwise, I would probably provide a container of plain water as well as the water with electrolytes, so the chickens have a choice. Then watch to see if things go back to normal when the weather cools off.
Of course post again if they have other symptoms. And hopefully some other people will read this too, and check what I've said, in case I missed anything important.