Didnt see this sorry. Lost the betta others are dying. They are all guppies now. I removed most of the snails in there, did a small water change, used prime Still dying. Why? I took half the fish out of there a few weeks ago. What changed ? All my other tanks on the same schedule are fine.Nitrates are way high. It's recommended they never go above 20-30 ppm. Betta will start suffer above 20. Your water is also alkaline. Most fish need somewhere around 7, but most can adapt as long as changes are made slowly. So as long as ph reading are the same out of the tap as they are in your tank fish can take larger water changes.
Mine comes out of the tap at 6 for ph and buffers up to 8 in my tanks, so I gotta be careful with my water changes on my tropical fish. I do them more often at less amounts.
You water is at the top range for hardness as far as what betta can tolerate.