You sort of hit the nail on the head when you said,
"They happen when I'm stressed or have low mood." Most people have "flare ups" of their sensory issues under the same conditions. For me, it's the tinnitus and Visual Snow Syndrome, as well as, auditory sensitivity. When the brain is exhausted and/or inflamed (lack of sleep, stress events, too many carbs, too much caffeine, too much socialization, whatever your triggers are) there is often an imbalance of excitatory and inhibitory neurotransmitters, as well as, an oxidant-to-antioxidant imbalance in the brain. It's the same phenomenon that can trigger meltdowns and shutdowns, mutism, etc.
https://www.ncbi.nlm.nih.gov/pmc/ar... of actively,areas have also been implicated.