thanks for that.
I do water the leaves to keep the mites under control.
we don't have downy mildew here in Aus, and I have never seen any powdery mildew either.
It could be another fungus, like septoria but this just doesn't have the look of fungus to me. we also have very low air humidity here and not much rain at the moment. fungus usually follows a pattern of the areas of poor air circulation being affected first, but this is the other way around.
some of the cones are starting to brown off and die before they are mature now also, in the same manner as the leaves.
This plant has a massive crop on it, but im not really that keen on harvesting it as i think its a bittering hop.
However I would really like to know the cause of this so that in future if I have the same issues with other hops that I do want to use, I know how to fix it.
How frequently are you watering the leaves? I wonder if you might be just washing off the powdery mildew each time. This is really boggling my mind because it really
looks like damage from downy mildew, and I wanted to challenge you on saying you don't have that in Australia... but all I could find was articles talking about how well Australia has kept it out! Are there any universities there that accept plant samples from the public for disease diagnostic purposes? If so, you may want to send them a sample in case you actually do have an outbreak. Either way... I wouldn't grow things out of an active compost pile. It's quite literally a breeding ground of fungi and bacteria that break down plant cells.
I don't think this is a deficiency problem. Deficiency is pretty easy to diagnose because, being an issue of chemistry, their patterns are pretty regular. It's not Calcium deficiency, that looks more like a bleaching between the veins. It's not a potassium deficiency, because while that does have a browning at the tips of leaves, it's much more uniform, and only at the tips, whereas you have browning throughout the leaf sporadically.
Too much sodium looks similar to potassium deficiency, but a bit more intense.
This does remind me a little of Apple Mosaic Virus, but there's no 'rings' forming, so I am skeptical. It can cause browning. Do you have any more pictures of infected leaves? I'd be curious if there is more of a pattern here.