I think your diagnosis is right. I was talking to Michael Dirr about this yesterday, and he said something about having recently noticed a different kind of fungal leaf spot popping up around the state, but he couldn't remember it by name. In general though, Cercospora is what we get here in GA- and treatment is the same regardless of type. At our nursery, we try to avoid chemical use whenever possible, so our two main weapons are quarantine and amputation- cut off as much of the affected growth as you can stand, (or as much as you think the plant can stand), remove all fallen leaves from around the base of your shrub, and try to cut down on spread by rinsing your gardening tools in rubbing alcohol when moving from plant to plant. As far as I know, there are no products that will cure affected foliage, but there are some that can help prevent it from spreading- here's a quote from an article I found on eHow: "Home gardeners may try applying fungicide products available at nurseries or home improvement stores, such as Cleary's 3336, Zyban or Immunox." I don't know anything about those products specifically, but I have heard that many of the commercially available fungicides do work fairly well. Cercospora is a real headache, and unfortunately thrives on the same conditions that make for happy hydrangeas, but with some effort, it can be kept to a minimum. Good luck!

grow_em_maters, "what would you recommend for killing the aphids?" To control aphids you can brush them off with your fingers, spray them off with a water hose, spray with insecticidal soap, spray with left over soapy dish washing water (not the kind from a dish washer), or use something stronger like sevin. I brush them off or use insecticidal/soapy dish washing water. "Are they related?" Possibly. The problem with the internet is that you can't see the plant and how it's been developing, etc. which makes problem diagnosis very difficult. Later I'm going to ask some questions that will help with diagnosis. I'm not going to be around for a few days, but someone may be able to help out. Oh, and don't forget your local extension service may be able to help. You didn't mention that the plants are wilted, stunted, have lesions on the stem, or other serious issues. Based on that and what I'm seeing I'm going to assume that it isn't a fatal disease like one of the stem diseases or late blight. But, that's based on an assumption and you know what that means. Therefore, the assumption is that it is a foliage disease, the result of splash back, or because of the aphids. So, based on all of those assumptions, don't pull the plants, spray with daconil (or similar products), try to cut down on splash back, and try to keep the lower leaves dry. Also, continue to monitor and observe the plants. The questions. How old are the plants? Have you seen any other problems like wilting or stunted growth? How long have you seen the problem? What are your watering habits? What other helpful information can you provide that I haven't asked? Good luck. Randy p.s. I'm also not seeing halos, concentric circles, and other things that are indicators of certain diseases which contributes to why a more specific assesment can't be made at this time.

Thank you for all the replies, they were very informative! In the '17 year Magnolia study' they state: The Glen St. Mary’ has a large brown-backed leaf that hangs in a downward position, revealing distinct, attractive veins on the leaf surface. The canopy is broad, dense, and pyramid-shaped, making it one. The canopy is broad, dense, and pyramid-shaped, making it one of the best selections for landscapes needing a large magnolia. The photos of the tree I posted does seem to have the leaves hanging in the downward position. Although I'm not sure if it is a pyramid shaped tree. And about the 'Majestic Beauty' they mention: ‘Majestic Beauty’. Its leaves are the largest of any in the study, but they also are the lightest green of all but the Aldridge strain with pale green undersides. Also, the growth habit overall is irregular, lacking any particular characteristic form. The seedling selections and ‘Majestic Beauty’ had the largest leaves overall with the smallest leaves on ‘Little Gem’. Cultivars ‘Bracken’s Brown Beauty’, Hasse, and ‘Little Gem’ had the darkest brown backs, considered highly desirable in the industry. ‘Majestic Beauty’, the seedlings, Aldridge, and ‘Smith Fogle’ leaf undersides were smooth and hairless (glabrous), which generally is regarded by the industry as an undesirable trait. In the pictures the tree also seems to have lighter color on the underside of the leaves than some of the other types and I'm not sure if the leaf undersides are smooth and hairless as stated above (I don't live close enough to the tree anymore to find out). I gueess it will take me a little more research to figure it out for sure. Thanks again for the replies and links, they've really helped further my search to find out which cultivater the tree is.

Alocasia cucullata was my first thought? Not sure what the issue may be but hopefully knowing the potential species of plant might bring up clearer answers for you