Tiles on acrylic tub are cracking

Hello everyone,

We have been living in our house for a year and actually had a great bathroom. But now in June the tile at the window (I suspect I had the hairdryer too close when the window was open in the cold) and in July two tiles on the tub cracked within a few days and I am really very worried about how this will develop. Before I contact the company, I would appreciate some input to be better prepared for the conversation.

1. Windowsill
2. Tile adjacent to the wall on the left
3. Ugly joint in the middle of the tub
4. Tile adjacent to the wall on the right. This tile first cracked about 7 cm, 2 days later the crack extended
5. Overview

I now have many questions.
Are these probably isolated problems that can be fixed by replacement?
Do I have to worry that all the tiles will crack – also on the walls?
Is the Styrodur carrier of the tub damaged when tiles are replaced?
Can the tiler say the quality of the tiles is to blame?
So far only cut tiles have cracked – can that be the reason?
The joint between tub and tile seems very compressed to me – is it the root of all evil?
And why only after 1 year???