Yes, probably overuse, it happens to so many instructors. Ours have taken to demonstrating more on their non-dominant side to avoid injury AND they insist we do everything on both sides!
I've found that taking arnica helps, and I use ginger (a natural anti-inflammatory) in my smoothies daily. Recently started experimenting with "magnesium oil", which isn't oily, it's water-based; it's the magnesium in Epsom salts that relieves muscle spasms. I spray it on the sore areas after a workout. I think it helps with recovery. I ordered mine from Amazon.
You might also try icing the areas that tend to get sore, keep an ice-pack at the studio! It's such a simple thing, one tends to think it can't have much therapeutic effect, but my PT always emphasizes it.