The smaller baby piece, will usually sink. Future full sized babies will usually float (though can sink too) and then rise..and then attach to the new forming baby...
My 'baby starter' is currently sunk half way, as I only kept a tiny piece for myself after this last mail out. A new one is forming over the lid of the brew, nicely though!
Just let the brew go a bit longer until the top of your container is fully covered, even if it's with a thinnish layer. On resultant brews, it will get thicker. If you don't go over I'd say 14 days, you can still drink the Kombucha, but if it's much longer.....don't drink it, as it will be very vinagary and 'predjuice' your taste buds against it!
Just wait for the next brew cycle to test it at day 7-10.