After some power outages, I went through similar. I was reminded that frags ship fine and may be without light and much circulation for several days. i did a 3 day lights out with minimal stress. Cut feeding to minimum, water changes, syphoning, aggressive GAC and GFO and later as things began to improve, began vinegar dosing which has provided marked positive results. It takes persistence and some time, some 5 months in my case to get everything normalized. It takes so little to upset the tank environment and so long to fix it but so it goes. Just stick with a basic plan and be patient.