Actually, it can hurt if you aren't careful. Changing the temps up can open the door for a respiratory infection. You don't need to drop temps and it'll be safer if you don't.
It sounds like one of your snakes just wasn't ready. Even though they hit a certain weight doesn't mean they will breed. I'm in the same boat. I have a female that was bred all last season and never laid. Give your girl time. She'll give you eggs when she's ready.