The Hibiscus stem wilt is probably unrelated, and might be due to a different infection (Southern Blight perhaps, though usually damage from that infection is more extensive) or to stem-boring insects using this native(ish) plant as a host plant. Prune wilted stems off for now, and you can look inside the cut stem end (slice it in half lengthwise) to look for indications of either borer larvae or staining from infection. If neither appears present, the issue might have arisen in the crown instead (the place where stems emerge from the roots).

The tomato wilt, if caused by infection and not soil moisture stress, is more likely to be fungal in nature than bacterial. Fusarium Wilt is the most prevalent wilt disease in garden tomatoes in Maryland. You can use the information in the linked page, plus our Key to Common Problems of Tomatoes page, to determine if this is a likely culprit. Southern Blight is another possibility (the same pathogen that can affect ornamental plants), though there are ways it can be distinguished from Fusarium if the fungus is producing spore structures.

As close relatives of tomatoes, the peppers may have contracted the same disease, whichever blight or wilt pathogen may have been responsible.

Squash, as cucumber relatives, would be more likely to have contracted bacterial wilt from Cucumber Beetle feeding, which is a primary vector for that disease.

If you are not already doing so, growing cultivars with noted disease resistance to bacterial wilt or Fusarium (as applicable) can help avoid future outbreaks, though you may need to try a bit of crop rotation to avoid infection next year if there is contaminated soil. (Usually, at home garden scales, crop rotation as a preventative tactic isn't as effective as it can be at farm scales, but it's certainly worth trying. Or, you can try growing vulnerable plants in containers, though that of course might limit plant or harvest size, or make keeping up with watering and nutrient needs more challenging.)

Miri

You're welcome!

Mushroom compost sometimes has a high salt content. (In this context, salt doesn't necessarily mean sodium; it can refer to any mineral residues, like those from unused fertilizer.) High salt levels can "burn" roots, which can impact water absorption, leading to wilt, or stressing plants enough to make them more vulnerable to pests and pathogens. There is a way to test compost (including mushroom compost), but it's a different test type than standard soil testing. As a quality control measure, businesses selling mushroom compost should ideally have test results available for customers requesting that information.

Perlite and vermiculite is intended for use in containers with potting soil, so in the ground, they provide fewer benefits and may degrade faster, so in future seasons, you can probably skip them. Were the soil additives well-blended with the existing soil before planting, or was the planting hole that new soil and the surrounding soil unamended clay? If not mixed together, the different drainage and moisture- and nutrient-holding capacity of the two soil types can affect root health and growth.

Miri

You're welcome.