I have 453 charge cycles, manufactured on October 6 2023. I slow charge once I get home in the evening, leave it on charge for the rest of evening even after it already reached 100%, and take it off charge when going to bed. I got two days worth of my regular usage last weekend before it got into battery saver territory.
If you can back all your things up to a computer and factory restore, to rule out apps and configuration problems, and the battery life still has problems, it really sounds like a hardware problem (or sub-optimal charging habits that degraded the battery quicker, at least.) If it also still happens on stock OS, then it also rules out GrapheneOS.
Don't be misled by the battery health stats; GrapheneOS doesn't actually support reporting the correct battery health percentage (yet? it might never be supported on older devices due to hardware differences) and will always show 100% regardless of battery wear.