Im a little worried that you have done too many things....flush here....add nutes there....so it's kind of hard to say. My first guess would be ph problems......leading to problems with everything else. You NEEd to check ph because if it is wrong nothing else you do will help.....just make things worse

do you have some sort of pet store or something near you? They have very cheap ph testers you can buy in an emergency. However.....do NOT use anything for fish to adjust your ph....only to test it.