[kylek]

My guess would be too many terpenes (or extra added terpenes). A recent trend has been adding massive amounts of these volatiles to the mix (purchased in bulk from places like trueterpenes[0] - which has warnings all over it) to create "flavor profiles" or to more closely mimic the effects of smoking flower. These are the same as the toxic essential oils that people overdo. Some are far more potent than others and definitely can cause reactions (even in non-asthmatics).

Stick to unflavored distillates.

[0] https://trueterpenes.com/