Sps Horrida and Millapora tips sliming and bleaching

[Dragon Wrasse]

Hello all,

I have had a large colony of horrida (melon sized) which has just started to lose flesh at the tips....it seems to heel up and grow faster than it is receding. The millipora (grapefruit size) is doing well except it is always sliming at it tips.
The tank has 8 turbelle streams so water flow is not an issue.

These two corals are downstream of a Ritteri that is perched on its own pedestal and not physically touching. There is also a fire coral (yellow millipora) that is up stream of these.

Any ideas

nitrate 0
phos 0
cal 400
alk 3.6 dhk
salt 1.025-26
everything else is doing well

any feedback is much appreciated

[Bugger]

Did you just upgarde light or ozone or carbon? Sounds like there bleaching cause of light. did you leave your lights on longer then usual?