More than likely the sediment and carbon filters are the ones if indeed your filters are clogged. You can disconnect the line just before the RO membrane and see if the water pressure seems to be the same as the feed water coming in. If it is noticably less then the filters are definitely clogged and should be replaced.
How well your RO filter works is directly affected by your feed water pressure, quality, as well as temperature. The lower the temperature the lesser the pressure and less water production through the filter.
http://www.freedrinkingwater.com/infocenter.htm