Can anyone please identify this disease which is killing our bush?

what exact bush is this

Does it look similar to this chlorosis example?

http://www.oakleafgardening.com/problems/inter-veinal-chlorosis-due-to-nutrient-deficiency/

As to actual diagnosis I would suggest a personal consultation with your planting zone climate feauures, and soil in mind. A great resource that I have used and highly recommend .....is your local Cooperative extension. These offices are manned by a wonderful team of master gardeners that know your local situation quite well. There's also email ( submit a photo) Q&A resources that have helped my concerns and questions many times. Consider googling up your local extensions office.

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I hope you can figure out your issue. Good luck, happy gardening!

Absolutely looks like an iron deficiency. Take some leaves to your local master gardener at a garden store and they can probably steer you in the right direction. Where I live it is a constant battle to keep this from happening to various plants. This is a black gumbo...old cotton and corn fields...that was never meant to support landscaping plants.

When you figure it out for certain, let us know what you learned.

I believe that it is a fungus and can be treated with Neem Oil sold at your local nursery’s. You should try and remove all of the affected leaves and spray underside, topside and base. Keep and I eye out to see how the new growth is doing. You can also visit a garden center or google the descriptio.

It is a fungus called "rust" and you can buy stuff for it at a home and garden center. Look in the section for roses. Hope that helps!

Looks like rust to me too

my Meyer Lemon tree had something that looked like that and my local garden center said it was spider mites. I had to spray it for a few weeks and that took care of it.

It looks like spider mites to me. I had them in some of my planting and treated them with neem oil with a very small amount of Sal Soap added to it. SS is plant based and biodegradable and helps the neem oil stick to the leaves of the plant.