Prcessed our first birds, now i have questions

So we processed our first birds. Wasn't much, just the roosters that were driving me nuts. a couple of EE's at 13 weeks
which leads me to a couple of questions
1) Is there such a thing as over scalding? when we were plucking them alot of the skin came off with them (or were the roosters too young and too tender as a result)
2) the chickens were very stiff while processing, Why did that happen and How do I avoid that?
Thank you so much