I'm so sorry to hear that your bag arrived this way. Without seeing the white patches myself, I would probably return and request a replacement. I have several
MG bags in the original vegetable tan leather and one of my black ones did get "ruined" after I spilled coffee on it and didn't clean it right away (I didn't notice it at first). The bag was left with some streaky white stains. Don't let this story of mine discourage you from getting this bag though! I love mine and literally just carried one of them yesterday. I have a large collection of bags including Hermes, Chanel, LV etc and I always come back to my MGs year after year. I hope
Farfetch can correct this for you.