Duncan Frag question

[Scubabum]

About two weeks ago I picked up a Duncan frag from my LFS with two heads. They immediately opened very large and were looking great. On week 3, Three more heads started to develop and now all five heads are extended but the heads look very small. I'm not sure if this is normal behavior or not when the Duncan is splitting. My tank is a 58 gallon reef ready with 2 Mp10's for flow.
Parameters:
1.026 checked with refractometer
Ph 8.28
Ca 440
Alk 9
Nitrate 7 ppm
Phos .30
Mag 1400
Temp 79
The Duncans are sitting at 150 par under a Kessil Ap 700 Led. Any advice would be greatly appreciated. Thanks in advance.

 

[TangingOut]

Yes, normal. The heads will grow bigger.

 

[Scorpius]

My Duncan goes through times of being small and big. They like to eat.

 

[Scubabum]

Thanks for the replies. I'm currently feeding 3-4 times a week. Glad this is a normal behavior and not yet another problem.