I'm not sure exactly what you are referring to as "skin tightening", but no matter...
Anatomically, a stretch mark is a tear in the deep layer of the skin. The superficial layer is intact, and so the characteristic appearance is seen- a thinned area through which you can see the tiny blood vessels under the skin, or the underlying subcutaneous fat.
Because this is what a stretch mark is, and because all "skin tightening" treatments target the collagen in the deep layer of the skin, you should not expect anything like this to work to improve your stretch marks.
I would find a surgeon certified by The American Board of Plastic Surgery and review your goals with them. There may be options for you, but I think this would be a waste of your time and money.