Like others have said, it's got to be going somewhere. Some places might loan you a leakdown tester, if not Harbor Freight sells em for like 86 bucks (saw it yesterday). I'm sure it's not dead accurate but it'll tell you if you have an issue.
I've got PRW rockers (1.65 ratio) with Rhodes lifters on my Magnum headed LA and it's pretty quiet in the valve train. I use 10w-30 VR1 oil as well. I've got another Magnum with stock rockers and some cheap lifters (they're from 2015 when you could actually get ones that wouldn't die in 10...
Do new and replace all 6. You'll know you've got all new injectors and it'll be good for while. I replaced mine in my '05 at 260k miles and put new injectors. Tubes and lines should be find if they're not damaged, just clean them thoroughly before rebuilding. I believe I bought Bosch injectors...
I honestly don't see anybody wear them anymore around here unless it's a very elderly person. They tried to report cases again during the fall/winter last year but most people paid it no attention.