I have had them do some weird stuff like this, usually its a very temporary thing and will correct itself assuming you maintain your parameters and the corals needs.
Some people believe that this is an indication that the coral is splitting, although I've had a frogspawn almost triple in size and never witnessed anything like that before. It could also be a form of reproduction too. Like mentioned above though these things usually just run their course given time with no ill effects to the coral itself. GL.
I have seen all my euphyllia do this at some point (have 5 different colonies). Typically it lasts only a few hours and back to normal. Never was too concerned and in all honesty thought it was normal behaviour.