Angels can be a bit more aggressive then the Gouramis. Especially if you have a breeding pair of angels. Pearls are the calmer of the Gouramis. I have had blue and gold Gouramis and they can be aggressive.It's good to know, the aggressiveness of the gouramis sometimes I think that it rises more than normal, they are very beautiful fish, I also have corydoras, but having angels I don't know whether to trust the gouramis.
Angels can be a bit more aggressive then the Gouramis. Especially if you have a breeding pair of angels. Pearls are the calmer of the Gouramis. I have had blue and gold Gouramis and they can be aggressive.
I am so sorry for your loss!
I don't think fish can get shocked by malfunctioning electrical equipment in the tank since fish aren't grounded but do see questions about stray voltage causing health issues but not death.
Maybe lack of O2 due to filter not running for an extended time or dirty filter spewing crap back in the tank after a restart?