I've gotten them to germinate in the past but lost them for different reasons, mostly from being eaten. Finally got one through the winter outside in the ground and something ate it the next spring after it started to leaf out. It was still so small. I think next time I try, I need to put some kind of fine wire mesh over them to protect them from rabbits, or grasshoppers or whatever it is that thinks they're so tasty.

I have two maples that look the same right now, along with many other plants in my yard. I spoke with someone at the nursery about it and was told we had a moth infestation that occurred due to a warm spring (happens about once every 17 years or so). They told me they're fine and next year everything will look great. I can't say for certain it's the same thing, but you may want to talk to someone at your local nursery about it, they'll probably have a better idea about what is going on in your area.

The planting looks perfect. Keep the mulch, it was planted both correctly and the mulch is an asset in many ways. It looks to me like your best bet would be to remove any branches that are dead and move on, literally. I'm not being loud to you but rather the opposite. Great tree, Dax

Just looking at a Blaze maple, could cause portions of crown to change color. (Joke) But seriously, Freemanii Blaze and Marmos crossbred between Silver and Red Maple, have become iconic for early fall color problems. Maybe because presently, almost 99% of trees produced in Nurseries today, arrive with root flares already too deep in rootball. I agree with what others had suggested, it might be a girdling root problem. Another thing that will inevitably shorten your trees lifespan, is that mound of Mulch/soil at base of tree. Here is link to this old house video instructing owners how to perform a "Root flare excavation" around base of tree. https://www.youtube.com/watch?v=fI12XNNqldA  A root flare void of any extra soil is so important (Mulch turns into soil), that Forest service suggests sweeping young trees root flare clean of any accumulating organic debris each spring. Also check for any flat spots on sides of trunk, especially on side where colorful branch is. Which is sign of girdling root. Hard sad fact, todays mulch mounding fad is expected to claim more lives of trees, than EAB and Dutch Elm disease combined. Also, black tar spot causes no adverse health problems to tree. So you can rule that out. Do you have automatic sprinkler system hit one side of tree? A one sided tree problem, is usually a root problem. And I can see branch above that one also showing some fall color. From my observations over last 20 years, Blaze maples that show this early fall leaf color, usually retain those leaves until true fall anyways . And seem to have that problem year after year. Since you watch tree year round, you have best chance to make good diagnosis. If tree does not have problem next summer, but does again year after. Document some details each year, like weather conditions etc.. Overwatering or iron deficiency was another possible problem someone else mentioned. I would think chlorosis would show in all of crown, or maybe root on that side of tree encountered some limestone. But usually other trees in same area show same symptoms, such as crown full of yellow leaves. You may want to check soil PH, just to rule that out. But know if this branch held on to leaves until true fall, its only a visual problem just like black spot is. Also, 20 year maturity point is time when owners learn if tree will live past 40 years. Or will continue to slowly decline. But I presently think, its not that serious. And even if you do remove offending branch, one above it is already showing same thing. Don't let anyone tell you a good pruning will solve things. And I think low branches can be most beautiful thing on a tree, unless shaded out. With all this info I gave you, answer might be in there somewhere...I belong to a committee at Morton Arboretum where horticulturist that invented tree is also from. So hopefully I will have chance to speak with him about your trees colorful problem. And please keep us updated about problem, since there are so many other Blaze maple owners facing same difficulty.