Check that the canes are stable, meaning that they don’t easily tilt or flop around when mild to moderate pressure is applied. The stability test will be a good indicator of the root system being intact or not. If the canes seem sturdy, try cutting away the brown heads, and be very mindful of keeping moisture level in the soil balanced, not too wet not too dry. If the plants' root structure is still viable, it should sprout new heads. Just be patient, it may take a while.