C. Ovalis browning at leaf base

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At first I was surprised the buds were still alive. This is not an expected development. I still doubt it's a disease, and more likely related to cultural issues. Leaf and bud loss is common in orchids in bud with insufficient water or humidity. Diseases are uncommon in situations of low relative humidity.

How long have you had this plant? The seasons have changed. Could the ambient humidity be lower with central heating?