I agree, the lower leaf on that phal looks desiccated. With new root growth when you repotted into the hydroton, you would think things would have transitioned, but things don't always go as planned! Just keep the humidity up and make sure you have good air movement like others recommended and keep your fingers crossed! It may need a lot of patience and TLC! Don't forget it wouldn't hurt it to water more often then you usually would with semi-hydro culture, it helps with the gas exchanges for the roots!