It's not likely all three batteries have failed simultaneously. If they are all losing charge at about the same time use wise Having experienced the same thing here in the U.S., I think it's safe to assume the charger has failed.
You could buy a new battery and run it until it's discharged and attmept to re-charge it. If it reacts the same as the others, you will have confirmattion the charger has gone t.u.
You'll find that buying a new charger is more expensive, if you can even find one, than treating yourself to a new cordless drill...