We don’t have the GH tester but I can get it. We have had the guppies for nearly 2 months and only issue is one of them being attacked recently (separate post in the emergency forum/thread). We got 4 mollies and 2 died quickly. Other 2 are doing good and that’s been nearly a monthI should warn you though - the vast majority of Scotland has very soft water, though a few regions do have hard water. You have guppies and mollies which are hard water fish, and if you live in a part of Scotland with soft water they will not do well.
Have you tested your water for GH?