There's endless debate about the brown curling edges with Salvia and to my knowledge there hasn't really been an agreed on consensus. Some have even speculated that its a genetic thing. I'm not sure.. it's certainly not something I'd be really alarmed about, but keep monitoring it. You could try changing your watering or environment a little and see how it responds.. but if it is already stressed then changing it's environment drastically/suddenly could easily kill it.
Could you elaborate a little on your growing conditions? What is your growing medium? How often are you watering it? How much light is it getting?
A light, fluffy medium is preferable with Salvia. Something well draining but also not too heavy. I use a mix of compost, premium potting mix and perlite with fertilisation every couple months and it is happy.
Salvia grow lore confuses me a lot.. some will say they do best with minimal watering, others that they need constant watering. Both parties are right funnily enough. I think it depends on the growing medium. I found with a heavier medium that minimal watering produced the best results.. I would sometimes go over a month without watering and it was still a powerhouse. At the moment I am using a lighter/fluffier medium and it is absolutely thriving with everyday watering.. What can be agreed upon though is that Salvia likes consistency. Once it gets used to it's environment/medium it will happily do its own thing and it can adapt to a surprising variety of conditions and still do well. Keep changing its environment (that includes it's medium, position, watering regime etc) and it will not be very happy.
I've had plants develop brown edges and then months later produce lush velvety growth.. below is a small cutting in January.. brown edges.. a few months later and you can see its a powerhouse. I moved it into my green house. At first it would wilt everyday in the heat.. after a while it got used to it and has been thriving ever since. Since the frosts will be coming soon I will move it indoors.. it won't be happy in the beginning, but will eventually adapt.