I do not see having two or more of them as cheating. Nor do I think of it as a big secret or any thing like that. I also do not believe they must know about each other. If it works for you, have at it. Just because you do not tell them does make it a secret. It probably just has had no reason to come up. Take from each of them what can help you. You pay them, that is the only obligation to them.