it is very common (and desirable) for paphs to spike and grow a new lead at the same time. greatly shortens time to next blooming. I find that those paphs that don't put up a lead while blooming will often rest for quite some time after blooming before starting to grow again. The production of new growth appears sporadic. Even on the same plant sometimes it will produce new growth while spiking, other times after the "rest". Big healthy plants will tend to produce a lot of new growth though.
Paphs are usually not as fickle as, say, phals when it comes to bud blasting. I say usually because it happens, and sudden environmental changes are one of the biggest culprits. High humidity will not cause it if air movement is good. However, the single biggest reason for bud blast is probably water in the crown. If you have good air movement, water sitting there in the morning has time to dry off and usually presents no problem. Water sitting in the crown in the afternoon/evening/night has a very high likelihood of causing bud blast.
Other reasons may include plant maturity (tried to bloom while too young and then realized it does not have the energy), sudden changes in plant health (i.e. root rot), and others.