I noticed for some time now that the oldest and older leaves of all my phalaenopsis plants look shriveled/flacid and are soft to the touch, whereas
the newer leaves are firm and strong. The color is fine (not too dark green) so they are getting good filtered light. These wrinkled-like leaves eventually turn yellow, although it can take months, and then die. Is this unusual and a symptom of some malaise and how can it be corrected? Thanks for any recommendations!

Michael