Amyloidosis AL Free Light Chains below normal.

I have had 6 months CyBorD and 8 months Darzelex maintenance for AL. My Lambda Free Light Chains have been at the low end of normal and Kappa Free Light Chains BELOW normal for most of my treatment. What is the danger of having too too low FLC's. Doesn't one need a minimum of FLC's as the building blocks for immunoglobulins?