I don't think your shrimp killed him, sticking with him running out of pods, it can take that long for him to eat them all, then starve when they are all gone, usually takes about 8 mos to a yr, and they don't always appear real thin. Shine a flash light in your tank when lights are out and see if you still see pods running around your sand. If you see them, i am wrong, and i may be, but i don't think your shrimp killed it.