I have not noticed the change in flavour to sour.
But yes they have changed both the formula and the packaging. There is a very big discussion going over it.
https://forum.jimmyjoy.com/t/disappointment-in-the-recent-lowering-of-protein-content/2324/54
Are banana and strawberry your go tos? So far, I thought chocolate and vanilla were better than those two. I do quite dislike fruit though.
Also you can still buy the old formula in the jimmyjoy sale. Luckily there is samples of both flavours you mention.