I find that I need much less powder with this machine, so that could account for the white marks. I've also had brownish marks on my towels which I discovered was due to a yukky build-up inside the door seal. I hadn't been aware of this build-up, especially as I regularly put a cleaner through the machine. I've never had this problem with any machine but, for some reason, the Nextra 7 doesn't clean properly. You have to manually clean in between the two halves of the seal after each day's laundry is done.
As for the door itself, fixing the above should also help solve the door problem. Finishing your day's laundry with a quick wipe down should do the trick, removing excess detergent/softener/etc, plus I always leave the door & drawer open for an hour or so to allow everything to dry out. If you do have a big build-up that can't just be wiped off, try using a non-scratch scourer &/or a little Cillit-type cleanser. If it cleans your shower, it'll clean your washing machine door.
Sorry this is so long-winded, but I hope it helps.
SusieQ
August 2010
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix washing machines.