The short answer is that quite frankly arm growth is tied to overall weight gain for you at this point. Charles Poliquin is one of the smartest coaches to ever write–although he does have a habit of saying things I would categorize as pseudoscience.so I wouldn’t take his words as gospel–and has stated that he notices it takes an average of 15 lbs of body weight gained to see an inch gain on the arms. For a tall long limbed person such as you, that might be even more (and probably is). That is with direct arm work like curls in there.
If you are doing stronglifts 5x5, you should not be deloading IMHO unless you are failing to get the all the reps at your 95 lbs. If you are failing to get the weight you need to get back to a weight you are successful with. If you are not failing and you ARE getting the 5x5 in without missing reps then don’t sweat the plateau, it will break when you eat more. Bench strength is highly correlated with bodyweight.
At your weight you need to be focused on gaining at least 1 lb a week. Preferably a little more, even up to 1.5 lb a week. If you are not gainjng at least 1lb a week, you are no eating enough. Period. This means you log EVERYTHING that touches your mouth, determine how.many calories.you are getting every day, and then add to that. 5x5 is a good program and I have put people on it before…in fzct one of my good friends is about 6’3" and has gained 35 lbs in 4 months. It works…if you eat and track it.
My 2 cents is that you do stronglifts as written, but add abs/back/arms on say a saturday after all your stronglifts workouts are done. Emphasis on back here, because having a weak one will hold your growth, and hence your arms, back.