Hey all, still a relatively new homebrewer, this is my 4th or 5th batch I think so far. This is probably a pretty common question but I thought I did everything to get as low of an FG as possible. I brewed an American Stout based on the all-grain recipe from Brewing Classic Styles but added some quick oats. Here's my recipe on BeerSmith. I do BIAB for mashing. I tried an overnight ~12 hour mash and no mashout at 154-155F, which had dropped to 144F-ish I believe that morning when I began the boil (forgot to write down the exact temperature but was definitely above 140F). I hit the estimated OG exactly at 1.076, but after 3 weeks my estimated FG was way higher then estimated, ~1.024 corrected for temperature vs 1.018.

So I'm stumped. I'm not sure this counts as a strong beer but it's the highest gravity beer I've attempted thus far, so I treated it as such. I pitched extra yeast, ~4g of Safale-05 rehydrated, oxygenated twice, first by shaking the carboy aggressively for maybe 5 minutes, then ~12 hours later more gently, and opted for an overnight mash instead of a 90min mash/10min mashout to hopefully increase fermentability. I don't have super consistent temperature control but I let it ferment in a cooler room in my house that kept it between 60-65F for fermentation, mostly on the cooler side of that range.

One thing I think I could have done wrong is the amount of brew salts and ph adjustments i did. I do have an old ph meter I got an amazon for fermentation projects way back, but I've never really used it and didn't have any buffer solution. So i was adjusting purely off the estimated ph in BeerSmith. This was probably a mistake and I shouldn't have added so much different salts and baking soda without actually checking my ph, I was stressing myself out a lot beforehand reading how extra important ph is for dark beers and how the roasted malts can affect your ph a lot. Since then I've only been adding a bit of gypsum and calcium chloride for flavor until I understand mash ph better.

So could it have been my ph being out of wack that affected the FG? But I was under the impression that ph mostly affected efficiency/OG and I hit my OG exactly.

It tasted ok though or at least not overly sweet, I was prepped for bottling so i just bottled it anyway with enough sugar for 2.8 vol of co2 and a little EC-1118 to ensure carbonation. Does that sound safe? The fresh wine yeast isn't going to ferment anything the ale yeast couldn't I assume and just go for the simple sugars I added for priming.

Thank you if you got this far lol I know that's a lot, and for any help!

Edit: water profile since it doesn't show on the link i put, and my bh efficiency was 68%, estimated ph was 5.55.