Adjusting Carbonation On Pepsi Heads

It’s been awhile since I had to adjust Pepsi heads, and I forgot which screw it was that adjusted the carbonation. My CO2 tank is full, but the pop doesn’t seems to stay carbonated too long after its poured. And it seems to be worse on the dark pop over the clear pop.

Any help would be greatly appreciated.

Just a long shot here but, on my machine there is a “carbonation” switch right above the heads. Sometimes it gets shut off by someone cleaning the machine. Does yours have one that you can check? Like I said, its a long shot.