I recently bought a pair of ws5 headphones. A friend told me to be sure and keep an eye on them because his would discharge while they were shut off. Well mine do the same thing. I'll charge them to full charge and a few days later there's only one bar left. What's up with that? Is that normal? Why would a battery discharge when it's off. Not happy with that at all. Any advice or insight would be much appreciated. Thanks!