Quartzite countertops water stain and poor seams

These quartzite countertops were installed 5 years ago. We had the fabricator back once (last year) to fix the uneven stone/seam and staining around the faucet. It's starting to happen again. They want $350 to come back. They did a shitty repair the first time.

In the third picture, another seam at my cooktop has the epoxy coming out.

Two questions : What epoxy are they using to fill the gap? Do you suspect the water stain is coming from the seam or a bad seal between the counter and the faucet and getting into the stone from the the faucet cutout?