Phal Orchids planted in driftwood

[Salixx]

How recently do you attach them to the driftwood?

Bud blast and flower drop can be a response to stress and changes in growing conditions. If you just unpotted and mounted them then I would think that the plants are lessening their energy load in order to better be able to adjust to their new growing conditions and are also a tad stressed from being unpotted. Both are totally normal responses.