Could be a shipped eggs thing. I have only hatched one batch of shipped eggs and did everthing the same as when I hatched my own. Out of 17 shipped eggs I got 7. That's only 41%. Almost the same percentage as you experienced with 3 out of 7 for 43%. My two other hatches of my own eggs where 100% and 72%.
I agree a broody hen is much easier but I do enjoy the excitement and sense of accomplishment when I hatch my own.
Let's celebrate your three new chicks and hope they are all not all Roos....just had to join in the
fun!
Take Care!