several possibilitys for you problem,
1-your food grinder is clogged with debris
2-the return water inlet to the pump is clogged up or
3-heavy build up of calcium/lime is restricting water flow to the arms
to check and fix the first two, you will need to un screw to lower spray arm. remove 4 t-20 torax screws, lift the top section out that will expose the cover for the food grinder look at the inlets and see if it is clogged with debris. next remove the torax screw (t-15) for the cover. remove the cover, this will expose the grinderif it is clogged you will need to take it out and clean it. this is best done with a medium needlenose plyer. you want to get between the blades and the screen. pull it froward(not to worry it is spring loaded) clean it up. re-installing it make sure the shaft re aligns, and seats properly. reassemble the rest, and check for better flow. you should hear a much better water flow. for the 3 possibility there are alot of dishwasher cleaners on the market. just about any of them should do a good job of cleaning the water flow. good luck and post your results