It sounds like you could've been stabilizing your shoulder blades a bit better for that class. This is pretty common, and over time it can bring about discomfort, pain or a pulled sensation in the shoulder or around the shoulder blades. Are you aware of how to use the stabilizers of the upper back to keep the shoulder blades flat against the rib cage when doing poses like plank and chaturanga? The main muscle to look at is the serratus anterior.
This makes me realize that we need a video for this! It's difficult for many to understand shoulder stabilization.