In the world of ETFs, there were some laggards to be sure, many of which provide exposure to niche market segments or industries that are imperiled. Still, some of this year's worst ETFs may offer investors rebound potential in 2020.

The California Department of Tax and Fee Administration has announced that it will increase taxes on the regulated cannabis industry yet again. The markup rate for the marijuana excise tax will increase from 60% to 80% on New Year’s Day.

Pot stocks just keep getting destroyed.

We definitely live in an age of fads. People just keep chasing the next shiny pebble, hoping that “this is the one”.

Not all cannabis ETFs perform equally well given their different constituents and below is the performance of each in September ranked from the best (-2.5%) to the worst (-18.5%).