my silver shark which is about 7 years old and is about 7inches, has just developed two white spots at the front of his mouth ,as if they were nostrils, they are quite fluffy, he is in a 57 gallon tank 4ftx2ftx2ft, i recently done about a2/3 water change and too make things worse my pleco died last night whome we have had for a number of years and everytime we put the light on 40w my parrot fish goes white what has gone wrong?