Yikes! I've never dealt with this myself nor do I know of anyone who HAS ... but JUST today I was reading several articles on fungus and that name kept popping up.... here are some links if you haven't tried to find the answer elsewhere:
This guy on youtube has a LOT of fairly good vids on cannabis - this is his on fusarium...
www.youtube.com/watch
If you don't want to hear him drone on, this is a good article: https://www.lahuertagrowshop.com/blog/en/how-to-prevent-and-get-rid-of-fusarium-in-cannabis/
The youtube guy has THIS on Pythium:
www.youtube.com/watch
And a really good article on it: https://www.growopportunity.ca/pythium-a-fungal-devastation-to-avoid/
GOOD LUCK - omg good luck!