how old is your current media? it has a duty cycle life. you can only use it so long before its time to toss it.
if you're not getting the results you used to, try some new media and see if that gets you where you want to be. also if you're not already - make sure you're adding a dryer sheet in to help pickup the garbage/dust to help keep your media cleaner over time.
you may also try doing your initial cleaning with walnut and then switching to your corncob for your final clean/polish state. walnut is more aggressive, while corncob is a better media for that blingy polish shine you're used to
as noted - if you REALLY want clean, get a wet tumbler. they're a bit pricey but if you catch the sales they're reasonable.
the frankford lite kit is on sale right now on amazon for only $85, $102 if you add their pins on too
tumbler (84.99)
https://smile.amazon.com/Frankford-Arsenal-Leakproof-Polishing-Reloading/dp/B07KT8NQS8/
2lb pins (17.99)
https://smile.amazon.com/Stainless-Steel-Tumbling-Media-Pins/dp/B077DPQR7M/
you dont need any fancy additives/products to use it - a $5 tub of lemi-shine (dishwasher spot preventing agent, available at walmart or any major grocery retailer) and a $2 bottle of dawn dish soap will last you YEARS. and stainless pins never wear out. i use 0.5cc (1/10th tsp) scoop (lee powder scoop) of lemi shine with 2qts of water in my thumblers and about a tablespoon of dawn. It'll blow your mind what 90 mins in that solution will do.
i would still keep your vibratory tumbler for final polishing (just for time efficency - wet cleaning/drying cycle is 3.5 hrs or so - you can clean resizing lube off and final polish in corncob in maybe 1 or 2 hours tops for most stuff, especailly after a wet cleaning), but these will get the gritty nasty out - and the inside of your brass will be cleaner than you've EVER seen it, and a wet kit also cleans your primer pockets for you if you deprime before you run them. having to never clean a primer pocket again is worth the investment in wet tumbling alone - IMHO.
yard sale a dehydrator to use as a brass dryer - i got mine for $5.
HTH