I have constructed two 6 feet by 19 inches shelves using 3 heavy duty brackets which have diagonal support , which is screwed into stud using 3 inch steel self drilling lag from spax. The floor of shelves is made out of laying 5 2x4 pressure treated lumber. The wall outer construction is drywall, the shelves are in garage with room upstairs.
There is no sagging and it feels solid after putting around 150 lbs my questions are:
How many can I add similar shelves vertically using same stud safely
Does it provide any extra support if I add a 2 vertical 2x4 from both sides of shelves edge to the ground