Phalaenopsis leaves turning yellow/ orange/ pink

[Wade Coleman]

So one of my phals that I’ve had for about 6 months starting to look really strange. It rebloomed for me this spring and it began to grow a new leaf and then suddenly the older leaves began to turn this pink/ yellow/ orange color and slowly started dying off. At first it was just the bottom leafs, but now it’s only got two older leaves and a small new leaf. I’ve never experienced this before and I just noticed today that another one of my phals is showing similar Symptoms. There is no evidence of pest damage, so I’m not sure what is going on here. Any ideas?