i honestly think your under watering them. your soil looks pretty dry in that pic and the plant still droops. i have never grown cannabis outdoors but i know you need to water more often then every 3-4 days in 80+ weather. first lift your plant to see what it weights. if its light then water it. also knowing your using diy cloth pots then i would very much think that that much exposure will cause the cloth to act like a wick and evaporating the water in the soil quickly. also check to see after you water it, if it perks up or stays the same. that will tell you quickly if its underwatered.