How to convert quasar flux time series from observed frame to rest frame?
This is not an answer, but it is too long to put in the comment.

I am not familiar with quasars. In general, converting fluxes from an observed frame to a rest frame requires following consideration: extinction correction, cosmological expansion, k-correction. I think the simplest form is $f_{rest} = (1 + z)^n f_{obs}$ where $z$ is redshift and $n$ is some integer depending on how to express the unit of fluxes. This considers only the cosmological expansion. But, I am not sure if this transformation is valid with your quasars because they might be too far that $(1+z)^n$ is no longer a good approximation.