Would nitrates cause this?? Sps help

Ok so I'm beating my head against the wall trying to figure this out....as of late after I pretty much had a tank crash due to a work schedule and lack of maintenance I am finally getting my tank back in order but all of the sps frags I have put in lately last about a week with amazing color but then they slowly over the course of a couple days lose all color in their flesh...the polyps still come out and are colorful but the actual flesh color just slowly fades to white??!! I can't figure this out here's some tank specs

300 marineland dd
4 mp40s
2 wp60s
1 hammerhead wide open on a cl with a rock lift/spray bar design
Reef octo sro 6000 external skimmer
125 gallon sump
3 250 watt radium halides 4-9 pm
1 4 bulb t5 11-4 pm
Iwaki wd70 return pump

Cal 450
Alk 9
Mag 1400
Phosphates 0 Hanna checker
NITRATES 20 salifert

Is it possible that the higher than normal nitrates are my problem?? I've been doing extra water changes and just started vodka dosing trying to lower them and it seems to be slightly working...I'm just at my wits end and am tired of wasting money on coral just to see it slowly die

I do have some leathers, mushrooms, and a few Lps like bubble torch and frogspawn that are thriving great but sps are not lol I've tried montis birdsnest and a couple acros which surprisingly the acros are doing the best

Any thoughts would be much appreciated!!

Thanks!!

Stewie