I believe that to be a different type of tunicate.
Tunicates in our tanks are fantastic. Well, they don't become a nuisance and typically die.... if one would call that fantastic. LOL! Some are simply gorgeous and you just enjoy them until they disappear.
The ones to the right are the "Colonial Tunicates". They have this little common community going on. They all can look crazy different from each other.
Then there's the "Solitary Tunicates", like the one to the left.
Tunicates are sometimes called "sea grapes" or "sea squirts". There are free-floating, planktonic ones as well as the colonial and solitary ones you have. Fascinating creatures, partly because unlike most inverts ... they're chordates.