Balance is an overrated idea, that leads to parents getting between kids and their passions.
Think about what it feels like when you're really in the zone, or experiencing a state of Flow. One of the trademark characteristics of this optimal experience is losing track of time. If you're knee-deep in satisfying work, game, or project - the last thing in the world you want is for someone to come along and tell you that you need to stop, for the sake of balance. If another adult did that to you, you'd find it disrespectful or insulting.
But we do this to our kids all the time.
If you're worried about balance, try broadening your view. Look for balance over a week, not a day. Better yet, over a month, not a week. If you are up to it, look for balance over a year. Or a lifetime. You will be more respectful of those humans you are raising, and they will get to experience interests deeply.