Lower back pain on one side

Went on my longest run since injury today (shin stuff that was weeks later diagnosed as peroneal tendonitis) - 10 miles, then did some yoga, and then a 45 min lower body workout with exercises prescribed by my PT (SL exercises like RDLs and drops, SL straight and bent leg heel raises, bulgarian split squats w no more than 20 lb).

I think the pain set in during/after the run or after the yoga, but I’m experiencing these back spasm type pains on the right side of my lower back? I can’t completely remember when it started. I went out for a walk a little while ago and started feeling the spasms.

I have a leg length discrepancy (left shorter than right, confirmed by former running specific PT, podiatrist had hard time telling due to lower leg angle), but today I decided to run with a heel lift in the left leg.

I’m currently using a Salonpas patch on the area on my back, tried some sciatic nerve flossing, theragun on glutes, TFL, hamstrings, quads…

I know weak core could be a reason, but is it possible that the heel lift in the opposite leg contributed to this pain? Would be interested in any thoughts about what this could be, suggestions, or exercises that could help. Thank you!