If you look closely you'll see what looks like about 1/8" growth on the edges. You can see there's a line where it looks like growth stopped for a little bit then started. How fast it gorwos depends on multiple variables. Starting with genotype, lighting, nitrogen and phsophate concentration and ratio. microbial load, water flow and even tankmates all play a role.
As far as being happy that's far more subjective and unfortunately growth and coloration are not good indicators. High phosphates may cause faster growth but faster growth is also implicated in a weakened immune system. Since flourescing and chromo proteins are made by corals to deal with less than ideal lighting conditions, as anitoxidants to deal with free radicals and to deal with pathogens or parasites and since "healthy" colored corals in the wild have been found to have unhealthy shifts in their holobiont color can't be used as an indicator of health either.