Any type of filtration needs some type of regular maintainance. RO filters work with cartridges thar eventualy need to be changed or they are no longer effective or get clogged and can result in a loss of pressure. You should be able to find and change them yourself. Take one out, take it to Lowes and try to match it, they should sell something compatible. Do that and see if pressure returns. If not you'll have to look at something else.