There are many possible causes of the ailing of the Japanese Maple. The simplest explanation for the wilting could be frost damage; most of Maryland experienced several overnight frosts over the past two weeks, and tender plant growth was vulnerable. Radiant warmth from hard surfaces (such as brick) can sometimes push plants to leaf-out a bit earlier than normal, making them additionally vulnerable to temperature swings. Since most frost-damaged foliage becomes "cooked spinach"-like in appearance (a bit mushy and dark), this is debatable as to being the primary explanation for your symptoms.

Was there any herbicide (weed killer) used in this bed or around the pathway by the door? Some herbicides can be absorbed by tissues in tree trunks or surface roots, which would result in leaf symptoms. Alternatively, drift of herbicide sprays can land on foliage an cause phytotoxicity (damage from chemical exposure). Depending on the herbicide involved and how it contaminated the tree, damage might be temporary. If the walkway is salted during winter (even prior years), built-up mineral levels in the soil could be starting to kill roots. Reduced roots would result in leaf and branch dieback as the plant's water needs increase with leaf-out, warming weather, and general growth.

Having landscape fabric over this tree's root system is problematic, due to the conditions you mentioned: soil buildup over the fabric. As this then allows weed seeds to germinate, this defeats the purpose of the fabric as a weed barrier. Trees and shrubs can grow shallower surface roots into this new soil, which is more vulnerable to drying out during heat and drought. Irrigation, which you mention, is helpful, but by the time a plant begins to wilt, the root damage has already begun. Ideally, the landscape fabric should be removed, but if roots have colonized it, this may prove difficult or impossible without causing root trauma. The benefits of removing it versus the consequences of some root damage may need to be weighed. Landscape fabric also makes for impossible soil moisture monitoring (the soil around the roots, not on top of the fabric) since you cannot dig down into it to feel moisture levels you so can tell when the tree needs water. Mulch breakdown into organic matter is beneficial for gardens, but this matter may not be helping to improve the soil below with the barrier in place. Soil microbes might be able to move between the layers, but important invertebrates that help break coarse matter down are probably prevented from helping to mix this into the existing soil.

Plant stress can make them more vulnerable to pests and disease. Many garden plants experienced stress in the past two years from overly-wet weather and a late-season drought last year. Wilt, root rot, and canker diseases can all kill off cambium (sapwood) which starves foliage of water and nutrients. When a tipping point is reached between water needs and water supply, leaves collapse. These causes can be difficult to differentiate, and are untreatable once having caused extensive damage. Ambrosia Beetles and other wood-boring insects also can prefer wounded or stressed trees, and by the time their damage is evident, they too may have significantly impacted the tree's health. You can examine the trunk and major branches for signs of cracks, sawdust, oozing sap, or emergence holes (as narrow as a toothpick or as wide as a pen). Examples and descriptions can be found in the links below.

https://extension.umd.edu/hgic/topics/cankers-trees-and-shrubs
https://extension.umd.edu/ipm/landscape-management-nursery-production/ambrosia-beetles-maryland
https://extension.umd.edu/hgic/topics/borers-trees
https://extension.umd.edu/hgic/topics/phytotoxicity
https://extension.umd.edu/hgic/topics/verticillium-wilt

It is likely that the dieback will need to be pruned off. You can wait to see if the branches leaf-out again in a few weeks; lightly scraping the bark off can show you if the sapwood appears healthy (green) or dead/dying (white/brown and dry). Green sapwood can sometimes take longer than foliage to die back from causal agents further down the tree, however, so you can check it each week. If pruning, make sharp cuts with either a folding pruning saw and/or pruners and loppers, depending on branch diameter. If the dieback cause was temporary, regrowth should occur and gradually recover the shape of the plant, though it will take many years to regain this size. We do not recommend treating the tree with any pesticide or fungicide until the causal agent is positively identified. A diagram for how to remove larger branches can be found under the section "proper pruning cuts" on this page: https://extension.umd.edu/hgic/topics/pruning-trees.

For the Forsythia, we have seen multiple questions this spring regarding dieback. There are a couple of issues that can cause these symptoms, along with frost damage.

White mold is a fungal disease caused by Sclerotinia sclerotiorum and is favored by cool, wet spring weather. Early symptoms include stem cankers followed by wilting. Splitting open the hollow stems will sometimes reveal a dark structure called a sclerotium inside (it looks like a black grain of rice). Another possibility is a canker disease, https://extension.umd.edu/hgic/topics/cankers-trees-and-shrubs. We are also investigating the possibility of some type of insect borer/beetle, although at this point we do not have conclusive data on this.

Management is the same in any of these cases. Prune out and remove affected stems and branches. Prune to improve air circulation within the plant canopy. Forsythia is a type of shrub that benefits from renewal pruning. After flowering - now - is the ideal time to prune these plants. A good way to manage forsythia is to prune out one third of the shrub (the old stems) each year. Here is our page on pruning, https://extension.umd.edu/hgic/topics/pruning

Miri