My Macbook Pro M1 (Max) 16 battery drains crazily fast

After 1 year of usage, about 100 cycles, my Macbook M1 Max is draining like crazy (only 4-5hr maxium on full charge) but the capacity is still 99%. And I only used it for surfing and youtube. I even tried turning on low power mode but it is no different. People told me to open less tabs, turn off bluetooth, use 3-4 level of brightness but it didnt work (besides, whats the point of using a laptop if you have to open only 1 tab, no bluetooth and low brightness). People say this thing can last for 10-11 hours or even 14 hours of light use and 7 hours of HEAVY use but mine no matter what the usage it can only last 4 hours. I tried watching only youtube today and it last 6 hours. The diagnosis is completely fine therefore Apple refuse to fix the machine. I doubt it is not about the battery but it is hardware default or something.

I remember there was one time I spilled milk (only a little) on the charging port, i cleaned it immeadiately, afterwards I had some problems charging as when I moved the charger for a bit it stopped charging, but it was fine several days later. But I noticed there is a pin in the charging port (out of 5 pins) that is kind of black compared to other. Do the charging port and the charger itself has something to do with the battery life?

What more can I do to investigate?

Thanks.