foot ik bone pulls mesh from other foot

I think I had this problem before long time ago, but forgotten what causes my foot bone to pull the foot mesh from the other foot. I thought I had jotted the solution down, but I could not find it. any help please. I believe it has something to do with my mesh, but I can not see or find the problem.

go into weight paint mode and cycle through your vertex groups, to isolate the offending group / groups, then in edit mode select the vertexes of the leg with unwanted weights, and click the ‘remove’ button for each of the unwanted groups.