Cattleya Growth Triggers

[mopwr]

Background: I have three seedlings of Cattleya Amethystoglossa, all acquired from Miranda orchids last year in the same order (all seedlings: one aurea, one coerulea, and one albescens). At the time I got them, they were finishing up development of their newest growth and then went dormant and have been so for (what feels like) many months now. Roots have continued to grow and they look all around good, but I figured I'd see new growths by now. I went to check and noticed that one is now pushing a new growth that's moving pretty quickly, but the others just seem to want to grow roots only until the end of time.

My question is this: Is there a specific trigger that Cattleyas look for as to when to break from dormancy and begin pushing new growths or is it just a matter of "whenever they feel like they're ready"?

For reference all of these plants are in the same conditions, literally next to eachother, so I though I'd see bud break happen around the same time, but the albescens variety looks to be about 2 weeks or more ahead of the others.