I would say your friend is quite right. 

https://pnwhandbooks.org/plantdisease/host-disease/vinca-spp-periwinkle-rust

Jay W. Pscheidt, 2019.

Cause The fungus Puccinia vincae has been found in all PNW states. An alternate host is not needed for this autoecious rust. The frequent occurrence of the rust on new leaves and other factors suggest that the rust may be systemic in the plant.

Symptoms Leaves turn chlorotic with inconspicuous leaf spots on the upper surface of the leaf. Lower leaf surfaces have dark uredinina where telia are also produced. Heavily infected leaves may curl upward and shoots typically do not flower. Poor winter survival once a bed of plants is infected in western Oregon.

Cultural control

• Remove and destroy infected plants or plant parts.
• Avoid overhead irrigation or apply such that plants are not wet for extended periods of time. In very dry weather deep water as needed.

As to your maple, it may have succumbed to Verticillum root rot. Unfortunately, your redbud is susceptible to this disease and frequently affected. The disease is in the soil. The main one here is verticillium. 

I am afraid the prognosis for both plants is poor.