I know this is a new thread but I'm new to the forum (just starting Stage 2

) and just wanted to post on this topic as I'm going through the same thing .
I was starting to get severe tightness in my lower back and discovered that the problem was because I wasn't doing enough proper warm up and post workout stretching. I also discovered that the problem wasn't so much in my low back, but mainly in my hamstrings that were tight even before the program and now even more so with all the extra weights.
oh yeah and not being able to afford a massage therapist at the moment

i make sure to use the foam roller post workout to roll under my back, thighs, hips, etc. it's not as good, but a girl has to do what a girl has to do.