Welcome to the forum! Bud drop on phals is often caused by a change in the growing environment. Cold draft especially can cause the buds to drop. Often when I buy a local phal from a supermarket the new buds drop after I get them home. Presumably the change from greenhouse to supermarket to my home is too much. The plant usually sends out more buds once it settles in. The other buds looks OK to me. Make sure you keep the temps consistent above 65 F if possible.