Welcome, CipherBug. I am glad you posted. Heck, we all have something to learn about plants and growing them, and ATP is a great source of information. Post away!
You said you are in MA, but please post that info so that it shows up on the upper right corner each time you post.
Even though spring is a good time to start doing plumeria rooting, the sun is still a bit low in the southern sky where you are, and being inside, in cool temperatures and (still) limited light, you are marginally in that "rooting-zone". I would think that the lack of evident growth is normal. Also some plumeria root far more rapidly than others. My 'Celadine' will begin rooting often within two weeks and my 'Scott Pratt' won't root for up to six weeks! Just be patient and know that when your plants can get more heat and more light, they will root faster. I don't root any of my cuttings until mid-April at the earliest, and I am in Mississippi. I also don't root any of them in direct sun. I use a greenhouse for this. Only when they have rooted and show leaf growth, do they begin to go outside. I gradually increase the amount of sunlight though. The leaves will often sunburn if you just throw them in full sun without acclimating them to that sun. I will have those outside get shade from 11:00 AM till 4:00 PM, and every 2-3 days, increase the amount of sun by an hour or so. That seems to work for me.
Good luck.
