Is my Corydora catfish dying?

My corydora sterbai has seemed to have lost his barbels well most of them he stll has to nubs but their very short and its bine about 2 weeks since i noticed but their only 4 montyhs old so will they grow with the fish i have pebbles not jagged but i have a rock structure built that does have sharp edgs. anyway today my cory is really faded in colour hes very active swimming agaist the gl is he dying or what i have 4 cory's and 4 tetras in my 20 gallon well filtered tank