bromide is a toxic halide that we are all exposed to, it competes with Iodine in the body so even if someone is getting enough bromide it can be displaced if they have a high bromide load.
How much potassium a day do you get? Salt is often demonized for water retentions etc but the real enemy isnt so much the salt itself its that so few people get anywhere near the potassium they need. This throws off the bodies salt/potassium ratio.