Trumpet coral is shrinking

[jat148]

Hiya,
A Trumpet coral that's been in my tank for about a month is shrinking. It doesn't look ill in any way, but it's just not as big as it was when it first arrived. Other coral in the tank seems to be growing steadily, but the trumpet is going backwards?
Has anyone else had a similar experience of this - I've never kept one before?
It's a 200L tank, and the coral is about half way up, in moderate flow.
Parameters:
1.025
8.4 ph
10 nitrate
0.12 phos
9.1 alk
1260 mag
450 calc

Many thanks.

 

[Mr. Mojo Rising]

Can you please post some pics of the coral? In white lights (turn the blue's off)

 

[jat148]

Here's a photo, but it's not very good. I can't switch the blue off.