Well that's good to hear. They say not more than 5%, maybe 10% of their food intake should be treats so they get the balance of nutrients they need from their feed. I have a hard time abiding by this, but I try!
Just curious... How did they do? Just a case of over distended crops? I wonder how much a chicken will eat? Do they stop when they're full or will they eat themselves into a coma?
They may be panting because it's getting warm. Chickens don't handle the heat all that well. I'd massage their crops a bit with your fingers, moving the food etc. around. If they are really hard, you may have impacted crops, but they probably will be fine.