Unhappy Ancora needs help

All

I have recently upgraded from a 200 litre tank with a total of 120 watts of
flouro (including 40 watts of actinic) without sump to a 680 litre tank with
200 litre sump and refugium. The new system has 450 watts of metal halides
and 120 watts of flouros including 80 watts of actinics.

Water conditions seem good.
Temp 25 - 26 deg C
SG 1.024
pH 8.3 - 8.5
Nitrates 0-5 ppm
Phosphates 0.05 ppm
Nitrites 0
Calcium approx 400 ppm
kH approx 150 ppm and slowly increasing

All fish, two anemones, and most corals seem to be doing well, however I
have a large Euphyllia Ancora which was sensational in the small tank, and
now seems to be slowly withering away in the big tank. I have tried several
positions, varying both depth and water flow, but it does not seem to
respond. It's too nice to lose.

Does anyone have any advice?

Thanks

Phil