A pour in pad will provide a lot more support than the leather pad. One thing that will help the hoof grow properly is to keep support on the frog. The pour in pad can help with this (there are also frog support regular pads), because the pour in goes all the way to the ground.
So, he rotated in May, didn’t get any worse through August. And now he’s recently gotten worse? He definitely needs to be the priority of the better farrier on the team. I don’t get why the farrier would think his apprentice would have the experience to handle this situation.
Maybe you could post over in Off Course as well asking for a recommendation for a corrective farrier near enough to you?