Corals dying and looking pale :-(

I have no idea what's going on with the tank. All my monti's look awful and taking a turn for the worst. As well as my candy cane and a few more. However others are looking great with growth. My 90 gal tank params are good in my opinion.
PH- 8.0-8.3 daily
Salinity-1.025
Temp: 77-79
Nitrates-0
Phos- .04ppm
Alk - 7dkh (API test)
Calc - 430
Mag - 1420

I perform weekly 5 gal changes using Kent salt. It's just weird that they started looking like this about a week and half ago. Out of ideas as to what it can be. At first I thought starving corals so I feed reef chili every other day and dosed elos amino twice a week. Here's a couple iPhone pics to show a few different pieces. The first 3 are some of the ones in bad shape.

 

How long have you been dosing amino's? Have you checked usual suspects like stray voltage, broken heater?

 

Flame Angel??:-/

 

been using it for as long as I remember with no issues....heater is brand new. and I haven't checked yet for stray volts.

 

it nips here and there but nothing serious. had it for over a year and never had issues unless it went rogue on me lol.

 

Any changes to water flow? Also, I've been reading lately that direct one direction flow can be hard on sps.

 

I've made that mistake before when I first got into sps actually. in this case there was no change in flow. and actually I just got home from work and noticed that they are kinda sorta looking better. I'm hoping it was the T5 light addition that fixes the issue and not water chemistry. Which goes back to thinking that the LED units might be going bad and falling out of spectrum.

 

I think I might be on to something with the cause. I decided to recalibrate my PH probe on the apex. And it was off by .25! meaning at night when it showed 7.9-8 it was really 7.65ish!

 

How long have you been using it un-calibrated?

 

last time I calibrated it was when I got it. I would say around April last year .