I've been banging my head against a wall for the last few months trying to figure this out. I'm completely out of ideas at this point.
Tank turned 2 years old in Nov, and was mostly softie dominated for a while. I had success growing a few monti's in it at the same time so I figured I would try my luck with SPS. To make a long story short I have had abysmal success so far. Every single frag I have put in it since has RTN. Some in days, some in a few weeks. It doesn't matter where in the tank I place them they all end up the same. But more recently It seems like everything else is declining as well. Recently lost two heads of Todd's torch, I have a favia that is losing tissue, I had to rescue my plate coral and move it to another tank.
I'm not dosing anything, at all, the tank basically consumes nothing as far as Alk and Ca which is a sign to me nothing is growing. Recently I've added more fish, bypassed the some of the flow through the filter roller, and removed everything but some purit I put in to potentially remove any contaminants. I feel like i've done everything. Checked for stray voltage, checked magnets for rust, ICP, mapped PAR, even went as far as raising my lights.
48x24x16 seapora rimless
Ati sunpower 6bulb
vectra s2 return
2x mp40
1x Gyre XF330
Clarisea Gen 3
Simplicity 240dc skimmer
Alk 8.0-8-5
PH 7.8-8.15 (I hate how low this dips at night)
Temp 77.6-78.8 (average is 78.33 according to Apex)
Po4 0.07-0.1
No3 10-15
Mag 1350
Ca 430
I make my own saltwater using a 5 stage RO/DI and red sea blue bucket.