If I were you, I'd put up a set of hoof photos for Sully. And current body shots as well.
Diets loaded with 'grass' are challenging to 'balance' to.
One of the ways to prevent chipping and cracks is to maintain the breakover frequently, plus bevel and roll on the hooves, but if he's in shoes, that's not done at all. Plus, trim cycle is usually too long between resets.