I tried that Barry,it isn’t coming off.I notice there’s a split on the leaf in the photo.
The new(ish)sessiliflora stems and throngs are green,but the older ones are brown with only the new offshoots being green.
Most aquarium plants are grown out of water in hydroponic systems. When the plants get put into an aquarium, the terrestrial leaves die and new aquatic leaves grow.
Make sure you have a good quality iron based aquarium plant fertiliser in the tank for the plants, otherwise they will use up their reserve nutrients and then slowly die.