why the leaves turn yellow and brown
Hello, I apologize for the delay in getting a response to you. I'm afraid I don't have super great news for you. Most likely all three, but for sure the first two images are of invasive trees that need to be removed.
The first image is buckthorn. They are prone to rust spots. It will not spread to other trees, but it should be removed anyway as buckthorn is on the Minnesota DNR eradicate list.
The middle image is Siberian Elm, also on the DNR eradicate list. It isn't prone to fungal diseases but is susceptible to elm leaf beetles. I would recommend removing this tree as well.
After consulting with another Master Gardener, I believe that the 3rd image is a honeysuckle. There are several non-natives that are, unfortunately, also on the eradicate list. It's hard to tell what species your tree is from the images, so I will provide some links for you to compare. It appears to just be stressed, not diseased. If it's either of the native varieties, that's great and you can leave them. If it's invasive, you should remove it.
Native species: https://www.minnesotawildflowers.info/shrub/wild-honeysuckle, https://www.minnesotawildflowers.info/shrub/hairy-honeysuckle