Hi Laura, and welcome to Pixls!
If I download DSC_0213.tif and look at its metadata it seems that you are using the rather old stable 5.8 version. First thing you want to do is get one that is more recent (have a look here]. Doing so might solve all your problems…
I’m able to see and load the above tif in the latest RawTherapee version and if I export it it is exactly the same as the input file. But you did not tell us what edits you did and maybe more importantly which settings you used to export to tiff. RawTherapee has 3 options to do so: 16 bit, 16 bit float and 32 bit float, you can also choose compressed.
But before we start to trouble shoot your issue, make sure you download and install a recent version. A lot has changed since stable 5.8 arrived 2 years ago.