@Emma it's definitely dirt, my in-laws muddy dog has been round 😆 looks clean but isn't! What's the method floor clear?
I use a steam mop. I love it and I have a dog. You can get them off of Amazon for pretty cheap
I use hot water and a mop with antibacterial cleaning products, I mop a couple Of times. I have a mop that has 3 chambers so the dirty water doesn’t touch the clean one.
A steamer!
I have karndean flooring so I can't use a steam mop. I use spray mop everyday and do a boiling water with mop and bucket once or twice a week. In my water I add, capful of dettol, zoflora and little bit of washing up liquid. My water turns brown and you can really tell the dirt from the floor has been cleaned. Spray mops, as convenient as they are, aren't very good at cleaning the floor on its own. It's more on the surface clean rather than a deep one if that makes sense.
Method is a brand - they have a wood floor liquid cleaner x
Are you sure it’s not the colour of the wood coming up? But I usually do a quick speed mop (the flash one) or if it’s a deep floor clean either the method floor clear or flash do a liquid floor cleaner x