Pain in lower back?
It might be worth seeing a podiatrist. Since having orthotics in my shoes, but legs, knees and lower back have been so much better. It's amazing how raising your arches changes the stresses on various parts of your legs.
That's interesting as I think I may have collapsed arches. I never really knew before but my friend told me she had and when she explained it I thought "well my feet are like that!" I have had hip problems since I was a teen which is hereditary as are the bunions but I have noticed since my op the hip pain has eased immensely and I do not have anything other than the odd ache on the "wrong" side since starting running again. I sound so decrepit...I am only 35! I will look into podiatrist, could be good anyway with my beautiful feet!
I got lower back pain around that stage of the programme and I think others have reported it also. It was tough but eased off after a couple of weeks - as far as I remember I put it down to adjusting to the programme.
Saying that, our feet are really important when we run, so if you continue in long term make sure you look after them I have fallen arches also and have other issues relating to my knees. If my arches aren't correctly supported it throws off the alignment of my legs leading up to my knees making these issues worse so when I run a lot it encourages problems to happen unless I look after both my knees and feet.