I recently bought a used RO unit from the LFS. Owner only had it working for 3 months then figured out he needed a larger one. This is a 300gpd unit. It had a section of tubing missing where I later found out this is were a permeate pump was. It has to membranes on it and 3 canisters at 20-40 miscrons, 10 microns and 5 microns. When I first got this unit the pressure ran about 55psi. I switched out the canister filters to the ones mentioned now and shortly after that my pressure has dropped to about 20-23psi. I'm looking to purchase a booster pump for the unit but before I do that do you think i should get new membranes for it? Oh also the production went from about 200gpd to around 60-80. Thanks