Sorry that I don't have a Stages sink (they're so cool!) and even sorrier that your marble is maybe etching but can you maybe do a quickie litmus test on your water? I think places that sell aquarium stuff and likely hardware stores would have test strips.

Our house has very hard water that was also acidic so perhaps a comprehensive water test (where you have to send it off to a lab) might be in order before getting just a softener. Our whole house system softens and balances the pH. Then we have to have an RO faucet for drinking/cooking as the rest of the water doesn't taste very good.

I have Epicurean cutting boards and a non-walnut salad bowl that I use Williams Sonoma Bee's Oil (beeswax and mineral oil mixture) that did pretty well against the hard water before the softener.

good luck!

I like to use the Boos Board Cream on my unsealed walnut. I use the oil, too, but I think the cream penetrates better or more deeply. It is denser and has beeswax in it. With either, I apply a generous amount and leave it on overnight.

I use the acrylic (?) cutting board daily as well as the narrow tray for storing sponges and what not. I have saved the walnut board as a nice piece for serving cheese and crackers. The reality is it is so pretty I don't want to see it get abused as a cutting board. It is also very heavy and not that practical for keeping over the sink where it would have to be moved for washing dishes! Like the other stages owners who have posted up to the board, I also do not use the ceramic mise en place bowls. though they are nice for serving snacks! they are too heavy and large to use in food preparation.

I also had my contractor hack off the rack hooks on the bottom of sink so that my silverware drawer could go under the right side of the sink.

i have no regrets getting the sink though - it is a fantastic size and I love having the slanted platform for preparing fish and meat

I also started with Boos mystery oil as supplied by the cabinetmaker for our black walnut counters. I found that it required frequent reapplication. It is a very light mineral oil seemingly useful for daily application to an end grain butcher block after cleaning.

I'm now using Osmo Polyx oil as recommended by Breezy Girl, and have found this product to provide a more durable seal.

Here is a link that might be useful: stages w/ cutting board

Whenever we make new cutting boards for home use or gifts, I typically set aside a place for it that it can stay for a few days, out of the way of everything else. I slop on mineral oil making sure that the edges/ends get covered well and leave it to sit until it's absorbed or until it quits absorbing. Flip and repeat on the other side. I'll do this until it won't soak in anymore and use a rag to wipe off the excess. Sometimes it will leach out oil afterwards and I'll wrap in brown paper bags to soak up the extra. For our boards at home, I wash in soap and water, immediately towel dry and let them sit out overnight before putting them away. Every couple weeks after they have sat out overnight, I will hit them with a light coat of mineral oil and wipe away the excess after it's had a bit of time to soak in.

I have butcher block in my pantry. I found a product called Howard Butcher Block Conditioner (can use on any wood product I think) which contains mineral oil and beeswax. You need to warm it (soaks in better) and then apply it. Took about 4 coats for the initial oiling but now I just give it a single coat when I think it's starting to look a little dry. You can find it online at Amazon but I actually found it at HD. Runs about $9/bottle. I've had a good result with it.

Boos factory is in my town and we have an outlet store that sells seconds. I purchased 10 cutting boards for dd that lives North to give to relatives at Christmas.

The clerk greased all of the boards with the Boos cream and bagged them individually. She said to leave them in the cream until we were ready to give away.

Try that for your board. You can get the Boos cream on Amazon.

Is it possible that the hard water is leaving deposits rather than etching?

Our whole house water softener was cheap---sears.

Well, I oiled the heck out of it. Then my dh brought home a non-Boos cream from the kitchen store. Seems to be the same thing. I massaged it on the board this am, and will wipe off before bed, flip it and do other side. I'm sure I've got it under control now. Maybe I will leave the cream on until the am, since red_lover you said they left on for awhile. Where is the outlet?

Try something with alpha-hydroxy.

It's in Effingham, IL.