Ho I feel dumb now yes make sense now maybe I should reduce it and see.KB/s is different than Kb/s....
4,096 Kb/s would equal approximately 409.6 kB/s in Blue Iris.
Go into your camera GUI and you are probably at bitrates of the 10,000 range on two of the cameras and 8,000 range on the other two.
After you made the HA changes above, reboot your system and see if it changes. Mine went high after an update and went back down and stayed down after a reboot.