PC, two of them are from plant nurseries and the other two are from Norman's Orchids. The one that lost it's flowers had not split, but last time I cut the spike all the way down! By the way, what is a Dtps?
Cutting the spike all the way down is fine. It's really just a matter of your method. You'll figure out what works best for your plants and your growing.
A Dtps. is short for Doritaenopsis. it's an intergeneric hybrid between a Phalaenopsis and a Doritis. i have one that likes to be cut all the way back when finished blooming and another that is much happier reblooming from the same old spike again and again.