When you get back into doing these things, take it slow.
You might want to do only one of the two suspected items at a time for a while… so if anything tweaks you won’t be left guessing.
Anyway, you really want to make sure on anything involving your back. Take as much time as you need to make sure you are always doing the lifts right, before you up the weight again.
Form breaks down with fatigue or maximal efforts.
Also, lots of people doing deadlifts can simply develop a painful tightness in the lower back. If you flex your abs, stretching your lower back, and things feel better, you may need to add in ab work to keep things balanced up.
Finally, I’m no expert in back issues, but there are some good articles here on exercise form, injury prevention and injury rehab. Seek those out for your best bet at good advice.