Rear springs mistery

[Kalchev]

Heyas,

Been lurking here for a while, great place with lots of helpful info. Am driving an A8Q 4.2 '99 for 9 months now and I'm loving it. Sure has some issues, albeit small.

At the moment I have a mystery on my hands - my rear end sits an inch or more lower than the front. I have a LPG tank instead of a spare wheel, but even empty the height doesn't change
Week ago I went on a trip with some friends - 4 of us with a full boot, and the height didn't appear to be lower than usual.

So I'm thinking I have a spring problem. I'll probably remove the springs next week and measure some, which will be followed by comparing with some second hand ones. Dealer doesn't want much for a pair of new ones, so that's a good alternative. Now, my issue is I have no clue what these paint markers on the springs are all about. Do I have to match them exactly right, what is the difference between differently marked springs?

Much appreciated