Chaeto bottomed out my nutrients

[reef seekers]

3 months ago I upgraded my fuge lighting from a cheap led Amazon light to a much more power light. My cheto growth was explosive and was working for what I needed. I left for a work trip 2 weeks ago and got back to all sps coral and 50% of my lps corals stripping/melting flesh. Tested the tank and my nutrients are 0 no3 and 0 po4. I’m assuming the chaeto was absorbing nutrients faster than I was adding them via auto feeder. I’ve started to increase my feeding slightly more than normal now that I can feed regularly to try to get nutrients back into the water, along with direct feeding and aminos. I removed the cheto and filter and socks for now to keep food recirculating through the system. I’ve turned the skimmer off as well.
I’ve ordered nitrate to dose to the tank I’m holding back on dosing phosphates.
I have been home feeding for 3 days and still have no no3 or phosphate.
Any advice on what I should do from here?

Tanks perimeters are
Salinity 1.025
Alk 8.5
calcium 425
Magnesium 1300
Phosphate 0
No3 0
Temp 78.5
Ph 8.1

 

[Spare time]

Can you run the chaeto light for shorter periods or under less intensity?