You have a nice collection of seedlings.
Now remember, these are meant to be TREES so they aren't going to bloom until they get a little bigger. Meanwhile, if you cut off the tip they will branch, but you forfeit the possibility of blooms for that year.
So I'm afraid PATIENCE is what you need......
By the way - Plumeria do not come true from seed, so when you say you have '5 Yellow Jack' what you in fact have is 5 SEEDLINGS OF Yellow Jack. They will be different from the parent plant and - this is the good part - they will be yours to name!!
Keep us posted on their progress