Phalaenopsis with yellowing leaf

[fscherlie]

Hello! I’m pretty new to orchids, and I’ve had this phal for almost a year. Maybe this a sort of dumb question, but I recently repotted it and there is a leaf that has begun turning yellow. I just don’t know what it is, too much water? Not enough water? Sunburn? Help!

[Dollythehun]

Probably old age. Lower leaves are shed naturally.