If it's been in bloom for a long time and you haven't been feeding, then it could be trying to suck the nutrients out of the older leaves to maintain the spike and the new leaf it's growing. The roots look good, but when they are white like that it's an indication that it's time to water again.
With such a good root system I would say that you have to water more. A good soak each time you water can help the plant absorb a maximum amount of water. Don't let the roots stay white too long before watering again. I have one phal looking a bit like that because it was underwatered by my sister. Even once it was back on a regular watering schedule the leaves never fully perked up again, they always stayed a bit soft.
__________________ Camille
Completely orchid obsessed and loving every minute of it....