Spots on leaves
We were not able to identify the tree based on your photos. This looks like a type of leaf spot but we can not say what. It is late in the season and no controls are recommended. Rake fallen leaves and discard to reduce any overwintering spores. You can send us photos next season as soon as you notice symptoms so we can see what you are dealing with.
PER MY QUESTION: I'm trying to take steps for next year but noticed several plants hot spots showing during the growing season
I'm sorry, but I was clear that I didn't intend to treat it THIS year, but wanted to get a jump on next year. From my reading, there may be preventative steps one can take; I have read that many of these do not treat spots/fungus/etc after they show.
I also noted that these are showing on many of my plants; inferring different genus.
Would you be able to recommend a preventative treatment (e.g sulfur sprays or copper-based fungicides or safe alternative if needed) ?
Raking up and removing infected leaves is a preventative step. It reduces the amount of infectious material in the area which would infect your plants next spring.
Any fungicide treatment and its timing would depend on the species of plants. Perhaps you can provide us with the infected species you have observed. If there are several species involved, they are likely to have different diseases, which would also require different remedies.