How to value Fancy Yellow Diamonds?

[JohnAC]

Hi all, I'm trying to sell a couple of loose fancy diamonds and wanted a second opinion on valuation.

I've been offered 5200 for the round and 5600 for the radiant, both per carat. Are these fair prices? Should I be looking to secure something slightly higher?

Thanks!! I've attached pictures of grading reports and photos of the stones.