Frank, no it isn't normal. Nearly all Blu-ray players have lasers which operate at wavelengths of 780nm(CDs),650nm(DVD/DVD-A/SACD)and 405nm(Blu-ray). These are the optimal wavelengths for reading those types of discs(contrary to the nonsense we sometimes read about "dedicated" players), and when in good working condition your Blu-ray player should read CDs(unless they're badly damaged)flawlessly.
The problem with your player wouldn't likely be a dirty lens, since the lens for Blu-ray would almost certainly be equally dirty. The laser diode for CD or its wiring may be failing, but whatever the problem would be, repair wouldn't likely be economically practical.
