Iron leaving brown marks

[Automaton539]

OK, so, I've seen lots and lots of people on different sites giving different advice and different reasons. But figure I'll ask anyway.

I have a new iron and I'm using ironing water bought from the local Sainsbury's but every so often the iron will splutter, sometimes feel like it's dragging (usually only when it leaves a large mark) and leave a brown mark, sometimes it's just a little speck other times it's larger and streaked in the same pattern as my iron's steam vents this is very annoying as I'm trying to iron things for a house that's on air bnb and booking. com so it needs to be perfect.

To add, I've found for the most part it only happens when the iron is set to full steam mode, doesn't (semm to, but most testing required) happen when it's at half steam, but some of the heavier creases are stubborn as hell and just won't come out on half steam.

It probably needs rescaling. Do you have a button on your iron for this? My iron occasionally does this but is sorted by some heavy steaming. Try on a tea towel first before your posh linens.

It needs descaling. The other thing is you can't use those scented ironing waters in some irons so check the instruction leaflet.

As far as I'm aware the iron is actually new, I'm not sure how it needs descaling already. Though, earlier after accidentally pressing for more steam when it was still cold then lifting the iron a large stream of brown came out, so I must agree it definitely needs a clean. Did my best to flood the steam vents shortly after, so hopefully should be fine.

I believe it does have a self clean setting, so next time I'm seeing to the property I'll give it a once over.