Your plants look really healthy. My first guess is they need more light. They all look very dark green. These type of phal orchids need to look light pale/yellow green when they get enough light. And if you have a purple/red one - the leaves will even turn a little red on the ends and underside when they get enough light to bloom. The temp drop should work well so I say - increase the light. Do so slowly so that you do not cause burns.