i dont think you will ever to get them to burn right trying it that way. If you want to run them all off the one regulator you already have then they all need to be high pressure. Now the only thing that makes these burners either high or low pressure is the orifice. So as I see it you can replace the orifices in the bg12 to high pressure ones, then all three will run off that regulator. Or you can convert the bg14 to low pressure and buy a low pressure regulator, they run at 11" water column which is about .5 psi. They are some advantages to running low pressure. First i believe it to be more efficient on the use of propane and also if you decide to automate in the future it is easier/safer to work with.