You will need to pass the array of handles edit to the callback/function where you want to access them all, and either:
- loop over the handles just like when creating the edit boxes, or
- simply get all values at once: get(edit,'String')
What you are doing now will only access one edit box, because when the callback thickness is called the input hObject only contains the handle for that one edit box that triggered the callback, not for all of the handles. Thus you need to pass all the handles yourself if you want to access them all at once.