In my opinion you are trading one necessary element for another and the end result is the same. It is just sort of early to expect much rooting or leaf growth. A combination of day-length and warmth is what gets those rooting-juices flowing. Just be patient. Also, resist the urge to water that perlite mixture. All you'll do is invite rot. I lightly moisten my perlite (and I use 100% extra-coarse perlite) when I first pot those cuttings up and don't water again until I KNOW the cutting(s) have begun to root. The plumeria really can't use water until roots have formed and leaves have grown anyway.
