Could be sun scald on the younger thin tree trunk. Try painting tree with white paint. The larger tree looks like it's dying/already dead.
Here's a link: https://www.gardeningknowhow.com/ornamental/trees/tgen/painting-tree-trunks-white.htm
Where in Canada are you?
I believe any acrylic water based paint is fine - but just to be sure, ask a nursery worker. If they don't know, google it. Orchard growers do it all the time for their trees.