I have been having problems with an arce buergerianum. During the past few months I noticed that its leafs are curling and turning brown. First I though that it was due to the heat at which I started to increase the watering intervals, but the issue continued. Now I think this might be due to a fungus. I been treating all my trees with insecticidal soap due to spider mites (seems they are freaking inmune to everything). The thing is that I did not know until very recently that it might be phytotoxic to trident maples and I do not know what could be causing the issue. Attached is a picture of the leafs. Any recommendation?