Q.Magnolia Stellata Looks Sick.
Branches look pale and very few weak flowers
Certified GKH Gardening Expert
They likely need feeding! I'd test the soil for deficiencies and feed accordingly. You could add an all purpose, but this isn't the best way to go about it. Just add what you need, and not what you don't. I notice the ground is a little yellow and more bare directly around the trees. I don't know if this is due to weed removal (We call it a weed-eater here), but if not, then it can be an indication of deficiency.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
Once you get the soil corrected, you will simply care for it properly. This will give you more insight to its care, though it doesn't require much:
https://www.gardeningknowhow.com/ornamental/trees/magnolia/caring-for-star-magnolia-trees.htm
