First off congratulations on entering three art quilts in any show! I never have the nerve to even enter. Second bindings are a huge item with judging. Last week I took a class from a judge and we happened to talk about the subject of judges and how they judge. In her opinion far too many only write up negative items. They don't explain what is wrong with the item, such as your binding. Instead in her opinion they need to explain what is wrong with your binding. She said the best judges explain what is wrong and often give very detailed explanations of how to fix the problem. She said that is how she learned. Also she tries to be sure and comment on the good points of any quilts she judges, not just the negatives.
Another point is lots of small shows are judged by just anyone. Not always by trained judges. She also commented on judges who judge by if "they" like the colors you used. Which has nothing to do with how someone should judge an item. Color use in it's relation to value, etc, but not if it's the judges favorite color.
So just go learn about bindings and see if you can improve yours in the future. Good luck and don't be afraid to enter quilts in future shows. I would probably skip the show you entered. Find other shows to enter.
Kat