Yesterday I went to the botanical gardens in my area, who had a gorgeous display last year in their salvia garden. But this year, several salvias are visibly suffering with lower yellowing leaves and lackluster growth (microphylla were fine however). About 10 large clary sages had leaves that were burnt and yellow, what would cause this?

I am having similar troubles with the salvias in my own gardens and wonder if this is related to the weather pattern? Anyone having a similar experience?