Battery Life Reduced From Short?
Batteries have very complex behaviour. (On top of that, playing around with lithium batteries can be extremely dangerous). There are many factors that influence what you're, measuring as the voltage:


battery condition. Most rechargeable batteries die when completely discharged
battery capacity (how do you know they're not fakes? Ie are they really 3.4 amp-hour batteries?)
charge state (how do you know they were fully charged)
load at time of measurement (was anything sinking or sourcing current to or from batteries while measuring voltage)


And in-between measurements: are you absolutely sure something isn't draining them? Some lithium batteries have internal circuitry that might be accountable. Plus that PCB you've soldered on, and anything else not in the picture. 

If I had to bet, then I would put money on one or both of these being the problem:


batteries are duds/fakes. Fakes are flooding the market, with 100th (just 1%) of the stated capacity. This makes over-discharging easy to do accidentally, ruining it - not that it was any use in the first place.
battery was not fully charged
battery is being drained