What does a judge consider to modify custody in Maryland?

I am the father of two young daughters and my ex-wife and I share legal custody of them. I am Turkish and when my ex and I planned to have children we agreed that our children would be raised in the Islam faith, as we were raised. However, in recent months the mother has not adhered to this agreement and is allowing our daughters to behave in ways that are not in accord with the teachings of Islam. I want to modify legal custody so that I can control their religious upbringing and ensure that they are raised properly. We live in Baltimore. What will a judge here consider in my request to modify custody? Is my former agreement with my wife regarding raising our girls in the Islamic faith binding and enforceable? Will a judge consider it important in a modification case?