There was nothing in the OP's original post that mentioned nutrition. You are entitled to raise your children as you see fit. The question for a 11yr old child was why his score was off on the back nine, I'm saying he or she is 11 and why even care if he is enjoying the activity. Different perspectives my comment was a little harsh for that I apologize.
Do your kids play golf?
I asked my kids instructor at the time, two years ago the same exact question the OP posed. I found it odd that he could be so good on the front and then start losing it on the back. He would be right around even par until around hole 14. He didn't have the ability to finish the round. Would always end up with a double and a couple of bogeys on the last 4-5 holes. Would be frustrated and angry at the way he played. First question his instructor asked was what was his diet like the day of the tournaments. I told him and he told me his mid was becoming fatigued. Cut out the sugars and lets adjust the diet.