Yes, pH and Alk are good.
In during further research, if I understand correctly the bromine tablets and powder add bromine to the water, but it won't show up in the readings unless activated by the shock. Once activated it will sanitize and consume waste compounds and in doing so deactivate and no longer be measured. I've seen reference to people adding shock to the tub every time they're done using it, not just once a week. I think given how much we've been using it initially, one shock treatment per week may not be enough to maintain measurable bromine levels.
Would love someone more knowledgeable to confirm if I'm on the right track or not.