Some corals dieing others thriving?Help

[frink]

Hi,
If anybody could help me out it would be great. I have had frogspawn in my tank for a few years and it has been doing very good. Growing very fast. Lately it is starting to recede to the point that I don't think it will last very long. THe skeleton is starting to erode away. I also have a mushroom coral that is not doing well. Here is the flip side. I got xenia that are growing very quickley and another type of mushroom that are doing well. Here are my water parameters:
Tank size 65 gallons
Lights: 2 x 96 watt compact flouresant
Salt 1.024
pH: 8.1
dkh: 8
calcium: 420
amm/nitrates/nitrites: 0
temp: 78
Other inhabitants include:
flame angel
lemonpeel angel
sailfin tang
2 perculas
1 cleaner shrimp
hermits and snails.
I have seen the lemonpeel nipping, but very seldom.
I have started to add essential elements and spot feeding my corals with a coral food with no luck. Don't know what else to do.

 

[reefforbrains]

Been keeping up on your water changes? Erosion of skeleton on stonies usually only is present when theres a lack of trace for long periods.

 

[renogaw]

I can't keep a mushroom to save my life, but can keep zoos, paly, and kenya alive with no problem. i've received 2 red and 5 blue shrooms in trades that didn't make it, plus i also bought 3 from lfs (thinking it was the shipping) and 2 of them disappeared last night and the third is shriveled up and will probably be gone tonight (i think something is eating them TBH).
but, these are all brand new shrooms, not something that i've had for a while. in addition to RFB's question, are there any parasites you may have introduced with the xenia and shroom? supposdely xenia thrive on nitrate rich water, is your test kit accurate?

 

[frink]

Thanks for the tips. I will buy a different test kit for Nitrates and see how that goes.

 

[dragonladylea]

I would definately get a second opinion on your water parameters, take some water to your local LFS and ask them to test it for you. Also, if you are doing a minimum of 10% water changes per week you really dont have to add supplements unless you have a large quantity of Stony corals.