If I can get humidity to 50% on a rainy day, even with a humidifier going full blast and large humidity trays, it is a good day. As Amy may not know I grow mostly Phals inside and the lack of humidity (usually 40-45%) doesn't phase mine and I never blast buds.
How long have you had this particular orchid?? If you just bought it and your home environment is new to it, then blasting of buds is common. My suspicion would be the heat mat. Your Phals will do fine in 65-70 degrees, and the mat is not necessary. A hot draft from a heater vent or cold that radiates through the window could blast buds also.
And one more question!! Does your Phal live in the same location all year, or did you move it to this east facing window once it began blooming??
Please update your user profile to include where you and your orchid live. Recommendations will vary greatly based on your climate.
And Welcome to the forum!!
