If both hot and cold are low at kitchen but ok everywhere else,make sure angle stops under sink are completly open. After that,it would probibly be inside facuet that requires taking it apart. That isn't an expensive facuet so it might be more expedient to replace it than repair.

This exact same thing happened to us, water pressure only low in the kitchen and the angle stops were completely open.
Next step is to check if the filter in your tap is clogged. Use a spanner to take the head off of the tap to check. Ours was clogged with little stones and shells. I dread to think what we have been drinking that didn't get stuck in the filter! We cleaned it using a toothbrush and pins to get the little stones that were really stuck in there.