Alright now I'm getting a little worried.
Came back to the tank this morning and the largest part of the split, is in the process of splitting again.
Nothing has changed in the tank. No real bio-load that can cause spikes. Steady feeding and 10% weekly water changes. Parameters are fine. Alk/mg/ca levels are the same as the salt that goes in it. I don't dose anything because it's an anemone only tank. No3 is at 5.5 and po4 undetectable. Salinity at a stable 1.025 sg with an ATO that runs perfectly. Temp stable at 25c 24 hours a day.
Do you have pictures? How large is the largest one that's splitting again?