all my gums in the yard are getting attacked by these dark red blotches on the leaves, i can't see any insects, just the blotches, which eventually turns the whole leaf brown, it then falls off. i have a 3 year old gum, which is almost dead, and now it has just showed up on another 2 year old gum, anyone now what it is and how to control?

here is what it looks like:

(unknown species of Gum - if anyone knows....)

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Eucalyptus ficifolia and Eucalyptus 'Summer Red'

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Eucalypt leucoxylon

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