Sounds like an electrical charge in the tank . I recommend a grounding probe and a voltmeter to eleminate the suspect then use the grounding probe as a precaution should something else go down... it is for your safety as well as the fish ... salt water is an excellent conductor of electrical current . I agree replace the power head ASAP
do you think the PH would change cause of that? land ast night when i caught my fishes they were all floating on top
Not sure what you are asking here ?
Still requesting perameters