Botrytis causes spots on some orchid flowers. The spores are everywhere in the air. There is nothing you can spray on the plants that will prevent flower spotting. There is no point to cutting off the flower spike. The best you can do is try to avoid cool, humid and stagnant air when plants are in flower.
This particular plant blooms just fine with very low humidity, so you could even bring it someplace with low humidity a few days before buds open. Botrytis wouldn't be as much of a problem.
Leaf spots are likely something else. B. nodosa is highly resistant to leaf spotting, so it may be old mechanical damage from a bump or a scratch.
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