Catteleya Hybrid dropping green leaves, is this normal?

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If the roots are soft and mushy, they should be cut up to where they are firm. If they are totally hollow and the outer cover just slides off, those are dead too. As Mira-Claude mentioned, it doesn't hurt to leave the inner string behind and they help anchor the plant. Anything firm even if it is brown should stay. sometimes they can get stained brown from the bark or what they are growing in.