Acer fungal issues - Again

[DamianTrimboli]

I have 3 acer palmatums affected by fungus. The leaves got burned (normal, is end of summer), the most burned ones fell off, and from those points new leaves sprouted.. but now, the younger leaves got burned in the tips too, and stopped their growth.
But do you suggest?
Thank you in advance!

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PD: Remember Im in Buenos Aires.

 

[baron]

Are they in full sun? Whats the temperature like? How often do you water?
Whats the soil composition like? From what I can tell from the images theres quite some green on there and it isn't moss?

 

[DamianTrimboli]

They are not on partial shade, but they don't receive full sun either, just a couple of hours a day.
temperature ranges from 20 Celsius to 30 Celsius (we had some 30+ Celsius day some weeks ago, but not anymore.
I water when top soil is dry.. usually is once each day, but some weeks every two days. Soil composition is just lava rock. the top dressing is sphagnum darkened with sumi ink (like Ryan Neil does), eventually it turned dark green.. I want to clarify that the moss is totally dry before I water.
I have several other maples that are exposed to more sun that these and they are not affected.. just normal sun burn.

 

[DamianTrimboli]

I would like to add that this Ilex Serrata might be having the same issue, what do you think?

 

[augustine]

Are your local bonsai people able to grow Japanese maple? Could it be too hot?

 

[DamianTrimboli]

Yes, there is no problem usually.. I have lot of other japanese maples that grow well.. all of the jap. maples have been grown from seed here, some of them has 30+ years old.

 

[Wires_Guy_wires]

What's buenos aires like in the afternoon? I've seen these issues with plants that have humid mornings and hot and dry afternoons. All I know about Argentina is that our queen was born there.
Not always a fungal issue, but more a 'drying too fast and getting heat' issues.

The damage on the ilex looks like necrotic tissue, this can be caused by insect bites.

 

[DamianTrimboli]

Buenos Aires is pretty much humid all the time, above 60% humidity almost always.
Argentina is big, we have all types of climates, from ice at the south to desert at north, with mountains on one side and coast on the other. I live in Buenos Aires, is a coastal city, so is mostly humid.
Im not sure the ilex issue is a bug, the black is on the tips first and it also happens on recently growing leaves. I almost lost all the branchs on one side of the tree, because eventually the branch die after losing all the leaves. (I think a bug issue would make it rebud if branch is left without leaves).