Newton - I see no injury due to excessive photo-exposure (sun). The first picture shows mechanical injury with some die-back of surrounding leaf tissues as a result of damaged leaf vasculature. The symptoms of sun damage are quite specific and don't vary much from plant to plant. Sun damage occurs in unacclimated plants when high light intensity levels cause chlorophyll molecules to rise to a more excited state than normal. If light levels are high enough, the energy that is released as electrons in molecules return to their normal energy state may be sufficient to form 02- oxygen radicals from O2. These are the same O2- radicals found in H2O2 (hydrogen peroxide, a bleaching agent) and are extremely reactive, readily destroying chlorophyll molecules through oxidation. The entire process and technical term is photo-oxidation, and we generally refer to it as sunburn. The initial symptoms are irregular patterns of silver or grayish coloration of leaf tissues due to the destruction of chlorophyll. These symptoms usually change quickly to obviously necrotic brown spots in most plants, but in plants with very succulent leaves the spots may first turn black.
The clear spots you see on the foliage near the maple tree are likely honeydew (excreta) from a scale infestation ..... probably cottony maple scale, but other species are a possibility. The honeydew very commonly acts as sustenance and a good growing environment for another pathogen called sooty mold, which blocks sunlight & slows photosynthesis in a direct relationship to how much leaf surface is covered.
The second picture leaves me wanting to say you need to look to the rhizosphere (root environment) and excessive water retention combined with over-watering as being causal of the spoiled foliage that wasn't obviously mechanical injury, which also covers the wilting issue nicely.
FWIW - I think fertilizers in the 2:1:2 ratios (as yours is) or 3:1:2 ratios are most appropriate for trees in containers, but because containers are fairly hostile environments for the micro-organisms that break down slow release fertilizers like your 4-2-4, you never know what fraction of the fertilizer applied will be available, or when. If you could find a soluble product in one of the same ratios, I think it would work better for you by virtue of the fact you'll know exactly what will be available, as well as how much of it. The other question is when, and the answer if you're using a soluble product is immediately.
I hope that was helpful?
Al