Battery performance seems to be dropping off.

Have a Chinese 20Ah Lithium Ion battery in pvc jacket for about 4 or 5 months. Lately it seems to take longer to charge. And it seems to discharge a tad quicker than it used to. Does that have anything to do with the onset of winter and the temperatures going down to 30 or so overnight in the garage? I'm not sure if its because I am riding faster now or if its the cold, or the battery life. I know that after replacing the failed Monarch fork with the OEM rigid mountain bike fork, I am definitely riding 2 to 4 mph faster than before.

Both cold temperatures and faster speeds will drain watts faster then warmer weather and slower riding speeds. For a real comparison you will need to slow down and get the battery about the same temperature before you noticed the drop-off in performance. Since it is moving to the cold weather then that may be hard to do, but that is what you would need to do a real comparison.

If you want to extend the range, slow down.

Be sure that you battery is in balance as well.

Could be dying, but once you are riding in 50F weather, that temp or lower will be very much noticeable less capacity. It may be taking longer to charge just because it's balancing more, or it could be even simpler. While discharging, the battery heats itself more than in summer, and there went some of your charge. Then of course, longer to recharge. Internal resistance goes up, when a battery gets really cold.

Also possible, a cheap o charger could have started out as a 250w charger, but now puts out 200w.

I wouldn't sweat it too much, but to test, gently warm your battery to body temp, like with an electric blanket. Go for a ride, and see if it feels back to normal. When riding in serious cold, starting with a warm battery, and insulating it during the ride can really help.