First time posting. I hope this is the right category to post issues with tiles…if not, please let me know.
Does anyone know what could have damaged these spotter tiles? In naked eyes, it looks like bird poop!

We remodeled our pool in November. We refurfaced the old plaster with stonescape mini pebbles, replaced waterline tiles, spa overfill tiles, and coping. For the most part everything went smoothly and the first fill was done before thanksgiving.
While water was being filled, I noticed the white marks on some of the blue spotter tiles. I thought maybe it was leftover cement of some sort and contractor should be able to remove it easily. I took pictures and shared with the contractor. Their project manager said they can fix it and 2 guys came over a few days later to fix.
It looked like they just brushed it snd the white marks were still there after they left, so I contacted them again. This time the pm said the white marks are not cement but it’s just how some tiles are. That means the tiles are like that when they installed them!
He then told me they can replace with better looking one but only after 45 days when the mini pebbles are cured. I said fine.
The problem is, for them to replace the tiles we will have to drain and refill pool again and we all know water is not free. I want the contractor to pay the water since they were the ones who choose to use the ugly tiles but they refused to pay for it and now stating that the water and chemicals might have damaged the tiles.
I don’t believe water and chemical can damage the way these tiles look and also it doesn’t make sense for water and chemical to damage just a few tiles and not all(the same tiles are used for spa overfill and none of them have white marks).
I’m thinking it was damaged during acid wash but there is no way for us to prove that. Sigh.
Any input would be appreciated and sorry for the long post!
Does anyone know what could have damaged these spotter tiles? In naked eyes, it looks like bird poop!

We remodeled our pool in November. We refurfaced the old plaster with stonescape mini pebbles, replaced waterline tiles, spa overfill tiles, and coping. For the most part everything went smoothly and the first fill was done before thanksgiving.
While water was being filled, I noticed the white marks on some of the blue spotter tiles. I thought maybe it was leftover cement of some sort and contractor should be able to remove it easily. I took pictures and shared with the contractor. Their project manager said they can fix it and 2 guys came over a few days later to fix.
It looked like they just brushed it snd the white marks were still there after they left, so I contacted them again. This time the pm said the white marks are not cement but it’s just how some tiles are. That means the tiles are like that when they installed them!
He then told me they can replace with better looking one but only after 45 days when the mini pebbles are cured. I said fine.
The problem is, for them to replace the tiles we will have to drain and refill pool again and we all know water is not free. I want the contractor to pay the water since they were the ones who choose to use the ugly tiles but they refused to pay for it and now stating that the water and chemicals might have damaged the tiles.
I don’t believe water and chemical can damage the way these tiles look and also it doesn’t make sense for water and chemical to damage just a few tiles and not all(the same tiles are used for spa overfill and none of them have white marks).
I’m thinking it was damaged during acid wash but there is no way for us to prove that. Sigh.
Any input would be appreciated and sorry for the long post!