Its all on the website/social media. https://www.thirlmerefestivalofsteam.com/trains
The five engines are:
6029 is currently out of action having a new tube plate fitted. 3237 and 5917 are both out of action at the moment. I know the 59 was receiving new driving wheel tires and presumably having other work done. I had thought 3237 was steamed last year after some remedial work but haven't seen any further information about it.