Can I take any legal action if my ex is allowing our 17 year old daughter to spend the night at his family's house?

My initial question would be whether she is being appropriately supervised when she's there. My next question would be how many nights is she spending there. The residential (custodial) parent has a certain amount of leeway but if the time is excessive, or if she is not being properly supervised I would consider going back to court to try to have the order modified.