Terracotta floor tiles cleaning / sealing

[paddyb2]

I have recently had a new kitchen put in. I was going to have a laminate floor put down, but after the builders removed two previous laminate floors, we found the original terracotta tile floor, which I much preferred to laminate. They cleaned it with some acid stuff, but the tiles still have marks on them and I guess they need vanishing or something to protect them? I’ve attached pictures showing the marks close up, what they look like dry and finally what they look like wet, which is what I’m after - the marks don’t show so much and they go better with my kitchen if they are a little darker and shinier.

There seems to be a bewildering range of tile cleaning and sealing products, could somebody recommend to best products and methods to achieve the results I’m after please? Thanks!