Water Quality

[midwest reefer]

Not sure exactly where to post this, but I figured here would be the best.
I have a 125g FO tank. It has been setup for years. Lately I have been having bad nitrate/nitrite problems. I have been increasing water changes, and it hasnt helped. Just recently(today) I added LR. Been meaning to do this for weeks but the curing process took way longer than expected. I added the rock thinking lack of bio filtration was my problem. I added roughly 40lbs of LR. My filtration consists of a sump with bioballs, and a skimmer. I have 4 bio wheels running off powerheads on the back of the tank. Also I have a magnum canister filter with a 25watt UV sterilizer. My fish consist of a 5" lunare wrasse, 8" porc. puffer, 8" stars and stripes puffer, 3" coral beuty and a 3 stripe damsel. I have a couple large hermits that do a decent job scavanging leftover food.
My question is.... what can I do to stabalize my water conditions. Any advice would be greatly appreciated.

 

[midwest reefer]

Also, I lost a maculoses angel today. He was covered in parasites. I tried to FW dip him but was unsuccesful. He had parasites (or what I believe to be) for a while, and so far still the only inhabitant to show any signs of illness.
Was the poor water quality a reason for this?

 

[pyro]

I doubt it was the cause of the parasites - anything added recently? The poor water quality probably just weakened the fishes immune system.

 

[midwest reefer]

the angel was the only recent addition

 

[chamic1]

Have you done anything different like start using a different kind of salt or changed testers or getting your water from a different source? If you have your own RO/DI /purifcations system, maybe your membranes need to be changed or the purification system is not running properly.