Blinking LED on AC Power Adapter: green light/ red light, slow recharge?

Once recharge reaches about 90% the LED on the AC Power Adapter starts to blink green and red. The battery icon also flashes between "Charged" and time of remaining charge. Flashing cycle dramatically increases time to fully charge the battery, as if it gets stuck in an infinite loop and can't reach a full charge. A few days ago problem started after the most recent software update. Battery has a mark of corrosion, one small rust looking mark. Power Cycle Count is 329. Unexpected shut down (not sleep) did occur one time when battery was at low charge. BatteryUpdater.bundle is Version 1.3. Battery was calibrated also a few days ago. MacBook is not under the extended warranty. Any idea if this is the battery problem or AC power adapter, or even a glitch in the recent software update?