My 18-month-old avocado tree has had a fungus a couple times, which I have successfully treated with a generic fungicide spray for ornamental plants (Penconazole, Dodine). It lives indoors year-round near a south-west facing window, and gets watered every 9 days.
I'm not sure if its most recent infection was a fungus or something else, but I thoroughly sprayed with the fungicide because about half the leaves were dying. Now ALL of the leaves are dying, and I'm wondering if the problem was the fungicide, or if it simply didn't work at all.
The first picture is an infected leaf before I sprayed, is this a fungus? The second picture is of one the last still-attached leaves two weeks after I sprayed, is this still a fungus, or did I cause the problem with my spray (or something else)?
I have a new batch of tiny leaves now growing, so I want to nurse them to health and avoid the same mistakes.
Update: here are some of the new baby leaves, that are already clearly unhealthy. Is this fungus, or something else? Some batches of new leaves look very healthy, but some are already half-brown like these.
Thanks in advance for any tips on how to nurse my tree back to health!