palmier a chanvres (trachycarpus fortunei)

[londoneye]

Hi

I bought one of above about 2 months ago, and I have kept it in a pot, because I haven't yet decided where to plant it.

About a month ago I noticed that the leaves had a few dusky blue spots on them.   Now, as mad as this sounds, the plant in question is very close to my washing line and I thought I had put something on the line which had run ... anyway, didn't notice anything of the same kind for a few more weeks.   

Then today, after rain for a couple of days, I noticed the same again (this time no washing has been out, so can't be that !!).    If it makes any difference the pot is currently sited beneath (or partly beneath) a pear tree.   

I was wondering if it is some kind of mould ?   The plant itself looks ok, but it doesn't seem normal.   Also I only put into normal all-purpose compost, and I am wondering now, also, whether palms need a particular kind of compost.

Any ideas anyone please?  The palm will have a final resting place, but not until August or September I think.