To keep them cool, you could freeze a half-gallon jug or 1 liter bottle of water, wrap it with a dish towel or pillow case & set that in there for them to stand near. Try the fan over the brooder & see if it helps, might be enough to just get the air moving for them. Adding ice cubes to their waterer too... I have some really cool ice cube cooler packs (like water-filled bubble wrap) that I used at the late end of brood-life for my girls, used to wrap a flour-sack towel over it & lay it under their mini perch so they'd hunker over it when they perched, this did wonders & they learned real fast what those wrapped things were! lol Now they're almost ready to lay & when it's hot out, I'll put frozen gallon jugs in pillow cases & lay them out for them, they perch on them, lay against them, etc.