That’s quite a Phalaenopsis collection you have there! Yellowing leaves like you’ve demonstrated in your photos can be a result of rotting roots. We suggest that you remove the Phals with yellowing leaves from their pots and carefully inspect their roots. Root rot can cause foliage to turn yellow and die off, and if left to continue rotting, the plant will eventually die. Healthy roots are green or greenish yellow in color and firm to the touch, while rotten roots feel mushy or hollow and turn brown in color. They may even smell bad!
Once you discover Yellow Orchid Leaves on your plant, here’s what you want to do:
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