I have a mini Lin Noelie in blue. I don't use her much in the winter so one spring I took her out and she had orange colored "stuff" near the bottom piece of leather on the fabric. I took hot water and a little bit of vinegar. Remember that vinegar bring the PH back to neutral but be careful how much you use. With light scrubbing and time, I was able to get all this "stuff" off.
Good luck!