Damage on Phalaenopsis leafs - what could it be and how to cure it?

[RosieC]

I wouldn't cut the old leaves off that plant.

Even if they look old and withered they are still doing something for the plant. Once they are not they will turn brown or even bright orange. I always leave them until they come away on their own with a gentle tug. Then I know the plant has completely finished with them and is willing to give them up. I never cut leaves unless they are sick (as with your previous one).