Can someone help ID what is plaguing my nishiki willow shrubs. These have suddenly turned on me. (on past 4 days)

We are in central indiana and we have had a lot of rain this spring, but also some very nice warm weather.

I noticed the browning is effect is only effecting areas that are NOT new shoots. (so the white new growth sections are not turning, only the older leaves along the stems)

I think my other nishiki died from this over the past 2 years. HELP I need ideas on how to investigate this further

thanks