Cannot edit the permalink structure and remove the blog slug

Hey guys, after updating to yhe latest version of wp, a new problem has arised. When i try to create a new post, i can’t edit the permalink structure in post editor . I have a multisite framework so, to resolve this issue i try to edit it from wp-admin/network/sites/settings, but i found that the permalink stucture over there is /%postname/. But when i try to edit from particular site’s dashboard setting, it is /blog/%postname/, how is this possible and neither i can edit or remove the blog slug. Is it related to hosting server?? Need a solution. Thankx in advance