Thanks for the detailed response..
The spots are on all irons
I usually (try to remember) to clean after each shot but do clean my after clubs after every round
Greenkeeper? maybe... It hasn't happened with my Mizunoo JPX 825's but then again that probably has to do with the different finish on both clubs..
Anyway a bloke from the golf club is interested in buying them, I have given them to him to try out for 2 weeks before deciding if he wants to purchase them..
Thanks everyone for the help.. We are having a rather unusual Autumn (Fall) here in Syd