Yellow/droopy leaves on Phalaenopsis

[GraceFace]

I bought this phalaenopsis three years ago, and am sort of amazed it has made it this long. Within the last three months though, it has dropped two leaves, and is about ready to drop a third one, all leaves have been at the base of the plant. After it dropped the first leaf, it began putting on new growth/roots that seem pretty healthy looking to me. Before the leaves started dropping, I was fertilizing on half the recommended ratio once a month, and just plain water as needed between fertilizing. I've since stopped so as not to add stress. The orchid is by a south east facing window, with profuse filtered morning sun.

Normal ? Suggestions ? Thanks in advance !