Sounds like you have a thriving business structure in place -- $1 million in year four is great. Well done.
Since you’re in a creative space, have you considered developing an app creation group within your existing business? Obviously you would need to bring in (or outsource) some specific tech expertise, but some of your current employees may be jazzed to join you on this side journey as well. Plus, when it’s successful, you’ll have a valuable addition to your agency’s suite of services.
Good luck and let me know if you need more assistance.