Why do phal buds not completely open?

[Paul Mc]

A friend gave me this phal last year after he had enjoyed it's blooms. He knew he would never get it to rebloom so he gave it to me. It bloomed late spring and has kept the blooms until they started to fall off about 2 weeks ago.

However, although it did bloom and there does not appear to be any damage to the actual blooms - they did not fully open. Only the outer 3 leaves opened, leaving the inner 3 leaves still somewhat closed around the inside of the floor. You can't even see the lip unless you pull the inner leaves open.

I'm curious what causes this as I have never experienced it before. The plant's leaves are full and healhy, so i was concerned about the roots and checked them. They seem just as happy, but I repotted anyway into a pot that was more appropriate for the massive roots size.

Any thoughts on why this would have happened?