Water temp can have a big impact on sour/bitter.
But also, it is a new bean and roasting methods to achieve a light or medium or dark roast can vary a lot too. That is to say, two medium roast batches of the same bean can be produced with different roasting temperatures and different development times and therefore they can taste quite different even though they may both be classed as medium. And different roasters have different ideas of what a medium or a dark roast is. Then, throw in even more variables in such as a new grinder or a change in water temperature…….
At the end of it all, if you like it then cross your fingers and try and repeat it.
I have a certain bean I roast the same way every time because I know that 9 out of 10 times I get heaven in a cup. The other roasts I play with different beans and different roast recipes in search of something different buy equally stunning.
My point is that there are a lot of variables when making coffee and your new and enjoyable discovery may be a result of some of those variable changing. See if you can replicate it as well as continuing to explore.