Jenn:
What part of California are you in ?
First my S x riverside does the same thing as it starts to get dry and the weather heats up.
But the Anthony Parker shows intervenal chlorosis on the smaller foliage which is usually a sign of a magnesium defiency but you show no sign of necrosis on older foliage(which is good). Try some phosphorus first see if that does not take care of the problem on Anthony.Riverside
I would not be to concerned greggi's go thru some leaf loss
as it gets drier.Replacing larger leaves (of Spring) w/smaller one for the drier conditions of summer.
Art

Thank you, Art. I'm in southern California, eastern SG county.

I was suspecting a nutrient deficiency because I haven't been able to keep up with mulching and feeding this year due to one thing after another. I hadn't done much of that in previous years either, and these Salvias thrived(?) in spite of my neglect.

I don't do much for mine either being we have plenty of (P)
Phosphorus and (K)Potassium. I just add a little nitrogen
and some Epsom Salts when it is cooler.
Art