Did you happen to transplant them into a different pot? I transplanted one that had an inflo and flowers one summer and the shock caused the buds to fall off and the flowers that did bloom were very tiny. I think it shocked the root system. The following summer it bloomed like crazy though.

Brighty

Nope, no transplant. I took the pots that I bought them in and put them inside something that looks a little nicer.

They seem to grow so effortlessly in Hawaii. Maybe the solution is to move there. :)

Plumerias are kinda funny sometimes. They seem to not like drastic changes in environment when they're actively growing. I suspect that's the issue. Can I ask where they came from? They were probably growing in a sunny, warm, humid greenhouse somewhere? They're gonna need part sun (like morning sun) and warm temps to come back. Since you're so dry, your sun is probably too harsh -- at least until they acclimate.

I bought them from a greenhouse here in Colorado, which I believe got them from a place called Jungle Jack's in Vista, CA. Perhaps this will be a matter of seeing how they do over time.

I've heard that it can be difficult to get them to flower again in Colorado and doing so requires some special care with the dormancy period, such as keeping them in a dark environment that's below 60 degrees. It seems like people do a variety of things during the dormancy period with mixed results .. I'm not entirely sure what I'm going to do as of yet. Any recommendations?

Well, LOL!, I've been growing plumerias for about 8 years now and still don't have them figured out. Especially the optimal way to winter over. I've kept some growing, made some go dormant, kept some warm, kept some cool, in light, in dark, blah, blah. The ones that are blooming or about to bloom right now, I kept in an upstairs bedroom, kept them barely moist, and they received some light from a West window. Room temp was probably around 68 degrees for most of the winter. The ones that went deep into dormancy were harder to get 'woken up' and risk was greater for black tip. Also, putting them outside during cool and wet periods raises risks as well.

...also, some varieties are just more difficult than others. Some varieties of mine just seem to be at higher risk for rot than others. Guess it's in their genes.

In Colorado your nights may still be too cool. You guys have some big-time erratic weather out there! What elevation are you?

If I were you, I'd winter it over in a spare room with some light, reduce watering somewhat. If and when leaves all turn yellow and fall, reduce watering more. But don't let the root ball dry out entirely. Then around Feb or March increase watering a tad. Don't begin heavy watering until leaves are 6" or so. That's my best advice.