I can't say what your problem is for sure but I just found young cut worms under one each under Rudbeckia Goldquille and two young Phlox. They hide during the day and feed at night. Phlox was heavily damaged. Anyway just thought I'd let you know. Young caterpillars maybe slugs but salvia isn't a slugs preferred food. Good Luck!

I have about 6 in front now. I purchased three new ones and plant in one area in the front. I had three in back that I moved and planted with the new three. This was in early summer probably. The new 3 did great last year where as the 3 I moved from the back yard just looked okay. They laid flatter on the ground and the flowers shot out in all directions (when they flowered finally). I moved them all AGAIN in the fall where they are today. They all look wonderful now and I even have seedlings springing up in the various places these plants had traveled to in the yard last year. Love it!

So.... my inclination would be that they'll bloom next year if they don't this year. Sometimes splitting and transplanting can hinder blooming for a season.

slugs eat the crap out of my salvia.
Put out saucers of beer and they will drown themselves in it --if they are the culprits.
Another trick I recently heard is to put the rind of half a cantaloupe in the dirt nearby (upside down, like a hut? ) and check it every day- apparently they will go hide there. (this advice was given by someone in a very very dry climate..... possibly won't work in normal humid gardens).