I would change out the filter media and your ph is 6? That is quite low. My water here is something like 7.2-75. I think 6 is too low for your fish. Something is defenatly wrong any problems showing up in the other fish?
Not really the LMB and the Sunfish are like whatever....I also have a 30 Gallon tank with Goldfish and their tank is just fine....So I know it not my tap water.....