The one I have seems to be performing pretty good maybe I'll just keep it is the coax suitable being 75 ohm instead of 52 ohm?
If the antenna is working, then stick with it. A new antenna of a similar design probably isn't going to work much better unless there is a physical issue with your antenna.
50Ω impedance vs. 75Ω impedance is a hot topic for some hobbyists.
Truth is, your discone doesn't provide a perfect 50Ω across the spectrum. And likely neither does your scanner.
In a perfect world where both the antenna and radio were exactly 50Ω, the use of 75Ω cable would add a tiny bit of loss.
In other words, don't get hung up on it. If the RG-6 is working, then go with it. Don't rip and replace with 50Ω cable thinking it's going to make a big difference in performance.
What I would suggest:
Take your antenna down and inspect it carefully. Pay close attention to where the coax connects. If it was not waterproofed properly, there can be some corrosion in there that will impact performance. Also closely inspect the insulator for cracks/damage. Make sure the elements are still tightly installed.
Also look closely at the coaxial cable. Pay close attention to the inside of the connector. Look for signs of water intrusion, corrosion, etc. If there's any signs of that, figure that water got inside and migrated down the cable.
Also, go over the length of the cable looking for damaged jacket. Any where the jacket is damaged, cut, abraded, etc. can be an entry point for water. Any signs of that would be a red flag.
If the coax and antenna are in good shape, reinstall the coax and waterproof it well while it's easy to access. Reinstall it.
If there's any questions at all about the coax, replace it with new stuff. RG-6 is cheap. If it is damaged, that will improve its performance.