My hammer looks ready to explode

[3rdMoon]

What would cause corals to NOT split? I’ve got a Hammer coral in my tank that’s been doing very well. It’s gone from a single head to 5 heads in about 6 months. Now tho, one head has swollen up like it wants to split, but for some reason it seems to have stalled out. It’s been like this for more than a month and it’s so swollen it looks as if it’s ready to pop. Yesterday I noticed one of my candy canes seems to have stalled mid-split also. Is there a particular parameter (trace element?) that I should be checking for?
Alk- 7.2
Cal- 480
Mag- 1400
PH- 8.1
Po4- .05
No3- 6ppm
Sal- 1.026
Temp- 78

 

[maleks.reef]

Do you have any leathers in your tank? Do you run carbon?

 

[helmsreef]

ALK appears low, are you dosing?

 

[TexanCanuck]

+1 on leathers ...