UPDATE
I Have been spraying the original cactus with fungicide. But it seems to be getting worse. The rot on the crown is bigger and there is alot more rot along the stem. Pictures below. Is it time to cut the crown off? Also do I need to remove the black from the sides? There won't be much cactus left.
I have also noticed the fungus is on my other cactus now. Pictures below. That all have it in the crown
I did quarantine the original cactus.
Would it help if the cactus were in full sun?
At the moment they are under a patio which gets direct afternoon sun.
Thanks
