simply check that tanks against another tanks.. if your getting 0s across the board ide say its likely your test is bad ect. as for getting 0s i get straight zeros on my planted tank regularly.. but i also have TDS issues with the tank and recently lost fish to this i believe( reason you should still do water changes regularly on them) idk if you have a TDS meter but ide check it if you can. what are your kh/gh on the tank? may have had a PH swing.. would also give you incorrect readings.
much as i hate to say it but did your son have friends over while you where gone? kids do stupid things sometimes, not always knowingly. as for the SB dieing from what i understand of them like other human bred fish.. geneticly it was probably a delicate fish. more delicate then your others.
much as i hate to say it but did your son have friends over while you where gone? kids do stupid things sometimes, not always knowingly. as for the SB dieing from what i understand of them like other human bred fish.. geneticly it was probably a delicate fish. more delicate then your others.