PO4 readings from nutrients vs leak

[BZreef16]

I cant seem to find a straight forward answer on this. Maybe a straight forward answer doesn't exist?

The concern:
I have a 5 month old tank that has had stable readings from day 1. I cycled with dry rock and a live rock from a 2-year-old tank and bacteria. I have had a BHA/diatom problem since post cycle and now have had a few bleached Acro's. I just cant seem to shake the issue and im concerned that a few 1-2-year-old frags are now bleaching.

Readings.
po4 .15 (Hanna)
No3 15ppm (Hanna)
temp 78
Sal. 1.026
Mag 1400
Calc 450
Kh 8.9
PAR 150-400

Feeding 3x day (nori and frozen foods)
SR80 Skimmer (overrated for tank size)
decent cleanup crew
weekly 10-20% WCs
Dose MB7 every 2 days.

The Question:
Lets just say that my reading of .15 p04 is from leaking rocks and not feeding/skimmer/etc.... If im trying to cut that number in half.... am i negativly effecting nutrients levels if they are already low. Im trying to correct by slightly less feeding and TM Elimi phos.

IE. Can you have low nutrients... but high po4? How can i gauge my po4 reading base on available nutrients. How would move forward if you were me.

NOTE: Regal is huge - in know. Working on a new home for him soon.

 

[Gumbies R Us]

It is possible to have high phosphates and low nitrates. I would keep a log of phosphates for the next week and see how they fluctuate.
Your acros bleachings? What is the light PAR where they are at? Do you have any inhabitants in your tank that could be bothering them?

 

[BZreef16]

It is possible to have high phosphates and low nitrates. I would keep a log of phosphates for the next week and see how they fluctuate.
Your acros bleachings? What is the light PAR where they are at? Do you have any inhabitants in your tank that could be bothering them?

I have been testing every 4-7 days and its stays around .17 - .12. Nothing in the tank should be bothering. Only crab i have is an emerald that i got from ReefCleaners. PAR where acros are is <400