Because they are dying. Phals usually bloom in cooler weather. They are forced by the growers for sale all year round.

Twice a week is more than likely too often for watering. Try once a week. Stick a wooden skewer down into the middle of the pot. If the bark looks dry, pull the skewer out and check it for moisture. If it is dry, it is time to water.

Phals grow on trees in nature and their roots are constantly exposed to the air. They LIKE to dry out. If they cant dry between waterings, they drown and rot.

If it is in a clear plastic pot, you can look at the roots to know when they are dry. They are green when wet, and silver when dry.

Roots that are watered too much turn brown and mushy. Roots that are watered too little start to look shriveled.

But, a general rule of thumb, I would say at around room temperature with average humidity, 4-6 inch pot with bark as the medium...once a week to ten days is good for watering.

Submerge the pot in water and then lift it out. Works for me. Be careful not to leave water standing in the crown of the plant or at the base of the leaves.

Your phal appreciates being next to the open window. They like air flow.