Brown spots on white miltoniopsis buds

[aerides]

This plant grows under LEDs about 12 hours/day. I run a humidifier and overhead fan on low during the day (not directly over the plants). Daytimes, it's generally 75-77 degrees, with humidity between 45-50%, sometimes maybe a little over. I turn everything off at night and open a window on the far side of the room a crack to help take night temps down to 55-60 degrees in winter (the conditions in which these buds developed). Thanks for your thoughts.