Pressure problem with Kohler shower faucet??

You probably have a water flow reducer in the shower head. It is a rubber disk with a few holes in it. Just remove it and put the shower head back on. They are installed at the factory to save our environment. (Mine are all removed)

just turn the water valve down some

Are you sure it's not just that the shower heads are getting dirty from calcium build up, thus reducing the diameter of the holes in the head, which will in turn cause spray to come out at higher pressure. ( same idea as holding your thumb over the end of a garden hose) Try removing and either replacing head, or soak it overnight in C.L.R (available at any hardware store.) and clean it good and try it again.

Probably some pipe rust clogged the exit.
If u have pretty low pressure on one or both, hot and cold water, try keep force closed by hand the water exit at shower pipe, then start both cold and warm water gradually as much as u can keep it closed with the hand.
The pressure of the water will try "escape thru the clogged pipe and hopefully unlock that debris or rust!
The hot water pressure going back thru the cold water pipe might unclog that debris.
Just a simple fix which many times works as a charm..
Otherwise if this is not fixing, try close both water from main service valve.
Then unscrew the secondary shower valves and manually clean them or replace if very damaged.

this is due to the high water pressure !reduce the pressure on your valve

Try draining the system and apply air pressure (min 30psi) to each faucet. Open other hot water faucets to allow pressure to vent. Next try draining and cleaning the hot water tank.

Sounds like it was installed upside down or the cartridge is installed improperly

ever since the pressure balancing regulations came out for shower valves, they have went from simple to very complicated devices. sounds as if some foreign material caused the valve to stop working. that valve is quit difficult to reassemble correctly because there is only one way it works and can be assemmbled many ways that do not work concerning alignment of the ports. if you dissassemble it and check that all the moving parts are functioning in the balancing cartridge you can then look closely at the alignment of the ports on the cartridge that the handle is connected to. understanding how the port align as the handle is turned should assist you in assembling it correctly......hope this helps.

This is a pressure balancing valve that needs both cold and hot water pressure to operated. It is an anti-scald safety operation.

Good Luck, Phil