What is happening to my steam generator pod phillips 740 iron?

My phillips 740 steam generator pod iron has started blasting out brown rusty water. it is virtually new and i had the same problem with a new bosche iron which i returned as thought it must be faulty. Now i think it must be the water or something I am doing wrong!
It was fine for the first 2 months or so. The problem does seem to be intermittent-ie once I have flushed the steam through until runs clear it is ok for a bit. I have rinsed the iron as recommended and was using unsoftened water but then tried softened water but it made no difference.