Laminar serum is a term sometimes used for the byproducts of inflammation that occur from the stretching laminae during laminitis. These fluids along with the dead laminae are what end up hardening into the "laminar wedge." The part that is dead laminae is somewhat rubbery, and the rest is as you describe, hard, yellow and resin-like.
Most likely what you are seeing is just part of the white line/laminae that appear yellow and can get lumpy when merged with the sole as the sole and bars grow. So my thought is that you're just seeing normal anatomy/shedding, nothing to worry about.