I agree with mycophline. Technically you're not quitting CT. You are making a big jump though.
I've used Kratom nearly every day for about two years, maybe longer. Sometimes I run dry for up to a week. Usually I don't experience WD other than mild irritability around day 3-4, but to me that's enough withdrawal that I don't want to experience it. Also, I've jumped around between brands and some brands are way stronger than others, even though a friend told me that all Kratom comes from the same place. When I don't experience mild irritability from WD, I sometimes experience fairly strong RLS. Like, not strong enough to cry about, but strong enough that it takes a few extra gabapentins to fall asleep in a timely manner. I usually experience WD like that from stronger strains.
You said you take 20-25 grams a day. Either your tolerance is really high, or you're getting some weak ass shit. How much I take a day varies widely, but usually one dose for me is a big teaspoon, roughly 2-2.5 grams. Over two years of taking Kratom and it only takes that much to make me feel goooood. I'm new to BL so I don't totally know the rules about advertising brands... But if anyone is curious about good brands, I've probably tried 10 different ones and found about 3 that I really like. If it's allowed, feel free to message me and I can recommend some decent kratom brands and strains.
Speaking of strains, your WD symptoms can also vary based on the strain you were using. For instance, if you used white borneo for 18 months, I wouldn't expect a very noticeable WD. But if you took red maeng da for 18 months, doing 20-25 grams a day, I would expect mild RLS WD symptoms and mild irritability.
Then again, everyone's biochemistry is different. Maybe you're just lucky and don't get WD from kratom, or maybe your WD supplements are really effective. Can you elaborate about how those supplements are supposed to help? Specifically the Vitamin C and the Phenibut.
Finally, going back to the stem/vein powder WD supplements, I've noticed with most drugs that I've used other than xanax, venlaxafin, and surprisingly gabapentin, that it doesn't take much of a drug to cancel out WD symptoms. Mycophile said "It's kind of like saying you are not feeling Oxycodone or Hydrocodone withdrawal cause you are on Codeine: a weaker opioid I had bad oxy WD once, and 2.5 grams of red maeng da made me feel like I was only have nicotine withdrawals -- strong cravings, but not much discomfort. Maybe a little, uh, disorientation? More like the world around me was kinda fuzzy. But it wasn't bad. Just the other day I asked a neighbor at the hotel I'm staying at for a cigarette. She was hungover and we talked for awhile. I learned that she was on day 4 of Heroin WD. She said that it wasn't that bad anymore, but when I mentioned that I was trying to get fucked up and only had Kratom, she got excited and asked for some. She was also hungover from drinking the night before on top of having mild heroin WD, but after she took (I'm guessing here) 3-4 grams of Kratom (biggest f*cking scoop I've ever seen for toss and wash), a few minutes later she was smiling and practically dancing while sitting on the stairs. Total mood change. Point being, your stem/vein powder supplements are probably making the WD non-existent. Again, it doesn't take much of a drug to cancel out the WD effects IME. Not for most drugs, including kratom.
But please, tell me about how Vitamin C and Phenibut help with Kratom WD. That would be helpful to know. I have lots of Vitamin C and I just ran out of Kratom. I also have gabapentin and klonopin, so I'm not too worried about WD symptoms. More so just curious about how vitamin c helps and what phenibut is. I've heard the name phenibut before but I have no recollection of what it is