Green Montipora not growing

[nuttyd]

Kind of confused by this. My green montipora frag has not shown any growth in almost three months. Doesnt look bad or dying, just no growth. Everything is flourishing including lps and sps. Parameters are stable. Dosing set. CA stays at 420, KH 7.8, Mag 1400. What could be the issue?

 

[Cyberdude]

Nitrates too low?

 

[nuttyd]

havent tested recently, but low nitrates would also stunt the growth on the other sps and they are growing like weeds.