Re: Possible cause for foot turned outwards (Steven Low please read).
Yep that sounds like psoas issue.
Messed up psoas tends to hurt the muscle itself or lumbar area in a plank position, and obviously can do the things you describe.
You can look for some videos on youtube and see if you can find some that teach how to do ART for the psoas...
Or just do a lot of mobility and slowly stretch/mobilize that sucker out