I've applied to several US grad schools for PhD math and one of my rejection letters stated that I can contact them regarding their decision. I would benefit from knowing whether their reason of rejection was something I can change (SOP, research experience, test scores etc.) in which case it might be worth applying again after improving those aspects of the application, as opposed to factors that I cannot improve on (past GPA, gap years, quality of past schools etc.).
Would it be okay for me to ask their feedback on this? One university has clearly stated that they do not provide feedback as part of their policy. Others haven't mentioned anything about this.