| Considering the problems with rot on cattleyas this year you seem to have little to worry about.
Black rot, if you had it, would spread and kill most cats in a few days. A famous grower of cats once said that all cattleyas have rot - it the plant grows faster than the rot it lives and if slower it dies.
I rate the health of my cats by new growth. You have new growth so the plant is doing OK. Black rot will often attack the new growth first and that is a bad sign.
You trimmed the leaves and bulbs of the plant you thought were bad and re-potted. The stress will often cause the plant to discard old leaves, when new growth is available to take over the support of the plant. It is not unusual for up to all of the old leaves to die as new leaves grow.
Actually my best personal orchids have only growth that started in my care and have lost all the old growth over about two years. Plants grow and discard old leaves.
Yellowing is the natural death of a leaf. Just be cocerned about the health of the new leaves.
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jerry  |