When Holmes and Watson discover the body of Mr. Talbott (at about 12 minutes 35 seconds) in his 'Love Nest', his right hand is at his right side, but when the shot moves to a close up his right hand is now almost touching the needle protruding from his left arm.
While talking to Jim Fowkes, Sherlock is eating scrambled eggs from a bowl. During the talk on several occasions the scrambled eggs appear and disappear from the fork. Also when the angle changes of the camera Shelock went from chewing his eggs to gaping with open mouth.
When they clip to a close up of the arm with the heroin needle in it, you can clearly see the syringe is glued to his arm/make up.
If Gary Norris had a severe peanut allergy that he was meticulous about, it would stand to reason he would carry Epipens with him at all times.
Watson says she has a mother who speaks Mandarin. But for her mother's generation, most Chinese in the USA would have spoken Cantonese, or some other dialect than Mandarin. Large-scale immigration of Mandarin-speakers from Mainland China happened only from the 1970s.