Phragmipedium Nicolle Tower
 

Photo for scale and then a close up. This is a sequential bloomer, very easy to grow, not fragrant. Flowers are long lasting and some years it sequentially blooms for 3 months. For some reason, however, the flowers tend to fall off, one by one, a few days after the newest one has bloomed, usually only holding on to a few at a time. Is that normal?

It gets a lot of water, and a lot of light, even direct in the DC area where I am.

Totally normal blooming habit. The flowers often still look fresh when they fall. But that's just what Phrags do.

if you want to preserve them for a few days you can put them in a clear sandwich bag with a moist paper towel, or float them in a small tray with water. they stay fresh that way!

It is what most Phrags do. A few will hold multiple open flowers simultaneously. One of the best I ever had, was a Phrag Cardinale (9 flowers open, between main stem and two branches).