This information is the best you have given so far. They are suffering from heat. Heat kills more birds than cold ever will.
The watery poop is from consuming a lot of water, but the lethargy and not moving much is due to heat stress.
Good suggestions by
@micstrachan cool water and deep shade. A small amount of watery treat like watermelon is o.k. but they need to be eating their chick starter. You can give them dry feed and make wet feed available as well if you like.
With your climate, likely you don't need a completely "closed in" coop, I don't know how yours is made, but a lot of people in hot climates have more of an open coop - still secured with hardware cloth and maybe having a couple of walls to help keep out wind/rain. Fans are a good option to circulate air, I use them in my runs and coop.
I also do not disturb my birds during the hottest time of the day. I do make sure they have cool water and feed is full, but no chasing/handling, etc. Treats are given usually very early or very late in the day during cooler times.
Pedialyte was a good idea. You want to get them hydrated. You can use that again for another day or so, or you can get some poultry vitamins like Poultry Nutri-Drench or similar. Once they have recovered, offer plain fresh water.