Sometimes it takes time for an orchid to adjust to changes in cultural conditions. Some Phals seem to be this way. I don't know how often you are trying different conditions (light), but if you frequently change that part of culture, the plants may be constantly trying to adjust and can't get their growth/bloom rythm going. Also, constant 72 degrees can be a problem. A temperature drop in the fall is often helpful in triggering blooming in Phals. In my experience, my Phals do better at warmer temperatures in the summer (up to about 85 degrees). I let them cool down to the 60s in the fall and get consistent blooming for the most part. Do you have photos of the plants and where they are growing? That may help.