Quarry/Ceramic Tiles Stained - Tile Advice

[Kerryes88]

We bought a property about a year ago and the bathroom has what I think are quarry tiles. Very recently every drop of water left on the tiles is leaving a dark water stain. I thought the tiles may be porous and that it may have soaked in and would dry out over time but the stains are still there. Does anyone have any advice on how to fix this? Have tried google but only finding advice on white water marks and other stains which doesnt fit here.