Stainless steel screws

I picked up the screws at my local hardware store so I have no idea what grade they were. All screws were covered in dicor. I used them to replace the ones that were holding the transition trim on. From the factory the transition bars were secured to the luan plywood and I ended up having to go into the aluminum substructure. I needed 2 in long screws otherwise I would have just replaced them with some from a rv store. So do I need to remove them if they are not the right grade? Last year I resecured the roof rack also since it was only mounted to the luan and the standoffs were loose. I used stainless screws there as well and secured to the substructure. Again everything is covered in dicor. Please advise and thanks for all the help!