Phil George explains in this video that questioning the faith or lifestyle of your parents needs to be done respectfully and honorably. You should determine what your standard or filter is that you're viewing the actions of your parents through. The Word of God should be your ultimate standard.

Ephesians 6:1-3 (NKJV) - "Children, obey your parents in the Lord, for this is right. “Honor your father and mother,” which is the first commandment with promise: “that it may be well with you and you may live long on the earth.”

I would start off by saying that no matter what direction you're coming from, that I think the Word of God and your conscience tells you that that's something that needs to be done respectfully and in an honorable way to your parents. And I would see there being at least two possibilities of what might make you question your parents faith and lifestyle. And one would be you're actually looking at the Word of God and using that as a standard to be able to look through because the reality is that we all have traditions and things in our life, including me and your parents and every other person that we know have things that we believe to be in accordance with what the Word of God says, but actually they're not. And so if that's the attitude that you're coming with with your parents, yes, still be respectful and honorable in the way that you're approaching it, but that's to be praiseworthy, that you would actually take the ultimate and only true standard and begin to assess your life in light of that. But if you're coming at it from a different perspective, a questioning perspective, a skeptical perspective, I would just ask you what standard are you using to actually try to filter your parents' faith and practice through?

The reality is that without God, without the fact that He's given us His Word, we don't have a standard that we can actually use to apply anything else. Otherwise, we're just picking an arbitrary standard that we're then using to critique the one true standard that God has given us.