high phosplates

hello again... something weird is happening in my tank. last week my skimmer over flowed and released all that gunk back into the water. i tested the next day and it read .07 using hanna phosphate test meter. i tested the next day and it read .05 after dosing some Phos RX. i changed my GFO as well as my chemipure elite. yesterday it read .10 and today im reading .12 NO4. nothing has died in my tank and not sure what is causing this to rise so much. i only feed 1 cube per day of baby brind shrimp and half a sheet of nori for tangs
tank is a few years old.

dkh 8.4
mag 1280
cal 460
nitrates .10 (usually zero)
phos .12