Hej Timmy!
Make sure there's plenty of flow for the Sarcophyton. They need to be able to shed their mucous layer, especially when they've been touched or transported. In the meantime, take a turkey baster (or something similar) and blow off the brown algae that's accumulating on it so that it doesn't get infected.
Have you checked your
nitrate and
phosphate levels lately? I see lots of bubbles on your rocks, which could be indicative of
cyanobacteria. Try to find out what the source could be. How often do you do water changes? What's your water flow in the system?
By the way, where in Sweden are you?! Har det bra!
