I can definitely relate, I feel so bad for them! Some damp soil in the shade helps with cooling too. A block of ice in a kiddie pool does too and my chicks played king of the mountain all summer lol.
When they’re chicks it’s hard to gauge how much isn’t it? As long as it doesn’t become moldy you’re fine so I would just keep an eye on it like you’re doing. How much wet mash they eat doesn’t matter, and with the summer heat I think it helps with hydration. I feed some to my flock every few...