If Dr. Carney is comfortable with doing it, I'd say it should be okay. This would make for a good Q&A submission for the
Medical Experts Opinion
(1) What fillers can be safely injected if someone has already had
(2) Does it matter how much of the original filler remains?
And so on. If you all have any additional questions to this topic (of different fillers in the same penis over time), post it here and I'll get some Doctors to chime in.