wood flooring graying/discoloring on 1st floor of townhouse?

It could be water damage or the finish is worn through. Wood will turn grey if it is not sealed. If water somehow sat on the floor for a extended period of time, this will turn the floor grey. I've seen this happen where someone let a potted plant sit on a wood floor, they watered it but protect the floor.

You can try to put a sealer over the gray area's but chances are you'll see where you tried to fix the problem. Possibly, a furniture re-finisher can do this and make the finish match the rest or the floor. If not the whole floor may have to be refinished. But if the damage was caused from underneath the floor, this may be just a temporary fix.

I'm assuming that there is a vapor barrier underneath the floor, if not then that could have something to do with the problem. Moister can ruin a floor from underneath. A worse case scenario would be to tear-up the floor and re-do it properly.

is there strong sunlight on this area? Some species of wood turn a grayish colour with UV light Walnut is prone to this.

Or are the areas in the places that get the most foot traffic? I would be leaning to the more to the finish having worn through than underfloor moisture problems. What do the areas feel like to the hand? If the finish has worn it should feel rougher that the rest of the floor.

All us wood flooring professionals should have moisture meters that can test for the presence of moisture, you may even be able to hire a moisture meter from your local hire shop! if you are hitting a blank with my other suggestions!

Hope this helps

After your latest up date

I'm leaning more towards the water damage. Wood floors expand with water, it sounds like it has and used its expansion gaps up so it only has one way to go and that is to form a hump in the floor. If its a vapour barrier problem the cost is a new wood floor plus a vapour barrier (sorry for the bad news).

How long has the floor been down? What's the floor underneath concrete, suspended timber..?

If its fitted recently contact the firm as they are at fault.

Your floor will get a lot worse soon if its water and a current problem.

I would rather have wood floors because there is a man and a 9 year old boy that live here they will not take their shoes off in the house, I think it's easier to sweep floors than to clean carpet

sounds like water damage to me. You'll probably have to sand a little, then stain the gray areas to match the rest of the floor.

have seen problem many times before, you need to sand sand back wood and reseal with a varnish that has U V protection. go to a good hardware store and they will help.