Cowboy~ I find your riding a little passive. I'm not sure where you are with him, but I feel you need to support him a little more. As mentioned, hands off his neck. By lifting your hands up, they become softer and help lift his shoulder. He's a little on his forehand now, as you go up in height this will be an issue. You can then softly push him into your hands to ask for collection/extension to a fence without speeding up. I think this will help with him backing off and chipping some of the fences. Really these are small fixes that take a 4th place round to a 1st. He seems like a really nice quiet ride.
The same would go for diamond. Lift your hands and teach her to collect her stride while keeping the power. She shouldn't need to fly at fences, it actually makes jumping high harder as they flatten out and go on the forehand.
If your horse says no, you either asked the wrong question or asked the question wrong
And God took a handful of southerly wind, blew His breath over it and created the horse