What are we looking at please? The picture doesn't have any context.

As above......we're looking at the bottom of the sink? Do you have water in/on the cabinet floor? Moisture in the cabinet floor? Do you see any surface damage to the sink from above at counter level?

If anything were leaking, there would likely be water. Whether sink, faucet, connections, the dishwasher hoses....SOMETHING.

Amerisink is a lower end sink...but seems a crack would be visible or felt, from above.

I have no idea what you are showing. Is this the sink from inside the cabinet?

No one can see anything from the photo, but if you want to know where the leak is coming from tape some paper towels at different locations, wash some dishes, use the sink and then check the paper towels to see where the leak is coming from.

The picture looks better if it is turned vertically. Can't make out what it is, but it looks better that way.

Thank all for your comments. My apologies for sending a very confusing and lousy photo. I am sending again a couple of photos.

Whoever did the plumming (this is a brand new kitchen counter), probably doesnt know what he was doing. i am afraid its a serious issue. its still under warranty … should i demand for a brand new sink? Since this is an undermount sink, do they

have to change the quartz counter too of the island?

By the way, the kitchen faucet gets loose and have to be tighten every now and then. Maybe it leaks when the faucet is loose

A loose kitchen - just when you think you've heard it all!

Thank you, Latifolia for calling me out regarding my mistake. I was in a hurry and didn’t have time to double check my message. Wishing you a happy weekend.

I repeat...........

Is there any water down below IN the sink cabinet?

Truthfully, I still can't really tell what is going on- if that is a water line stain and the silicone has gaps at the counter level, it could be that. Again.... it could be minor unless you see WATER or moisture and if the faucet "needs tightening" call back whomever installed it. For all we know, it's much ado about nothing. What brand is the faucet, where was it purchased etc? What part is loose, handle or base of faucet at counter level.

There are no mind readers here, and no...none of these issues have any affect on your counter tops.

Basically? Your best bet is call the plumber on the whole thing. If the under mount sink has no strap beneath? Have him address that as well.

Let's see how the sink is attatched to the countertop please; take a shot standing back far enough that we can see the countertop on both sided and all of the drawer in the front also.

That doesn't look like a leak to me.

Can you slide a steak knife between the sink flange and the bottom of the stone? Try a few places please.