Ammonia spike now what?

Was cleaning the back of the 28 gal nanocube and knocked the temp probe out of water. Tank overheated a week ago, soft corals didnt make it and they caused ammonia to spike. Removed corals, but ongoing battle with ammonia. Been doing 50-70% water changes every time ammonia gets to 1ppm or above. My guess is that the initial spike from corals dying caused a bunch of worms, pods, etc to die and its now rotting away, removed waht I can see...did like 5 massive water changes. what am I missing?

Teated source water and salt mix. both are ammonia free.

parameters:
sg 1.024 (calibrated ATC refractometer with lab solution)
ph 7.8-8.0
temp 77.5f
Ammonia .2-1.5ppm (red sea test kit)
Nitrite 0 (red sea )
Nitrate 0.75 ppm ( red sea nitrate pro)
Phosphate 1.36 ppm ( red sea phosphate pro)
Magnesium 1200-1300 (red sea pro)
Alk 11.2 (red sea pro)
Calcium 420 (red sea pro)

-tank age: 2.5 years
-coral, none all died. :(
-3 pepermint shrimp
-yellow watchman goby
-2 ocelaric clowns
-5-6 hermits
-snails, none all died, removed what I see
-sugar fine sandbed, 2-4"
-20-25 lbs rock, dead sps coral type
-28 gal nanocube
-reef octopus 2000 HOB skimmer (clean daily, about .500" yellow, brownliquid)
-Vortec mp10
-reefkeeper lite
-8 red mangroves
-Retrofit LEDs from RapidLed (aurora puk)
-1 gal reactor running Seachem De-Nitrate at 30 gph
-Seachem matrix carbon (bag)
-Seachem Purigen (bag)
-Seachem phosguard (bag)
-Water source : RO/DI for chloramites

what is my game plan?
obviously keep up with water changes.
Should I use Prime, etc to detoxify this?
Should I get some nitryfing bacteria to help out my overwhelmed liverock filter?