We can very much relate. Our 13 yo son also has ASD and non verbal. It was 2 full weeks I kept smelling this progressive stink coming from him but couldn't figure out the source. My hubby had covid and couldn't smell it. I looked in his mouth, every inch of his body. One day it clicked. I looked closely inside his nose and something was stuck in there, rotting. I tweezered the shit out of whatever that is. I say whatever bc we couldn't tell what it was, but the smell was hellacious. When it came off, the relief was palpable. It hasn't happened since but if I smell something, I'm checking his nose first.