If you have a local dealer to test water and balance you up, great. Otherwise, balance the water first yourself. Go out and get yourself a 1lb. bottle of spa chlorine, dichlor. Chlorine is compatible with bromine. Add about 1 cup of the spa chlorine with jets running and spa cover off for 1 hour. Remove your filter(s), hose them off, put in a bucket of water with 1/2 cup spa chlorine, let stand for i day. Put bucket out of reach of small children or a dog tempted to drink it. Test spa to see if you have a free bromine/chlorine level. If you do, the next day reinstall your filters after hosing them off well.
By the way, by adding spa chlorine to an existing bromine spa, the chlorine instantly turns into bromine but with some extra kick.
That should do it. If not, drain it. Super-sanitize that filter and start again.