Jup, gotta have some if ya sealed. What ppm are ya at?
I used to get the droopy look when my regulator would go bad an dump a tank when it got stuck. They need o2 as much as co2 an an imbalance will suffocate them like im seeing. Just sayin from my own experience.
Plants do opposite at night an if there isnt sufficient o2 then they droop from Co2 overkill in sealed.