Xenia's are strange corals, you can have a tank full that are thriving, change nothing and they all melt away in 2 weeks. Wait 6 months try again and they thrive again. Lots of opinion as to why but they are all guesses. I would do nothing and if it doesn't make it, wait 6 months and try again. I have them growing in low light, high light even got a couple of small ones that are growing on the ground probe wire in the sump. Most are in pretty good flow. I also do not dose iodine for them or anything else in my tank, just water changes.