Hi Paul. Yes it is very important to work the lower back to balance your workouts. Just also be aware not to overtrain one certain muscle group, especially once you add more resistance. Your body is giving you a warning sign, to rest up a wee bit. You will also find by resting you will progress more with your results.
Some lower back exercises for home: lye on your tummy, head facing down, arms in front, legs straight. Keeping your head down, lift opposite arm and leg up and alternate each time. Keep it smooth and slow. You must not rotate your hips. Stabilise through your trunk. Squeeze your buttocks as you come up, and keep your feet flexed and not pointed. You can also try one on the swiss ball. You may need to anchor your feet first, lying face down on ball, try to balance more on your hips. Start head down, hands near your ears and come up slowly, rolling through, without going up too high. Try only body weight first, before you add extra resistance. Remember muscle fatigue is fine, joint pain isn`t. All the best! Kind Regards Rachel.