Tomatoes often get curly tops when there's a big difference between daytime and nightime temperatures, which usually settles down after a few days, as the weather gets back to normal
![wink ;)](https://chat.allotment-garden.org/Smileys/green/wink.gif)
Other than that it could be bought in compost that has been contaminated with weedkiller in the green waste they've used. There was a lot of this about last year, but I haven't heard of any cases yet this year.