Sick Fish (Clown Fish & Blue-Green Chromis)

Ok, I've had a FOWLR running for 6 months (since adding fish). About a month ago my female clown fish's color very slightly lightened on the upper part of her body and about 48 hours later she died. My male clown fish was fine.

Well here I am today noticing that my ex-male (now female) clown fish seems very lazy and has also developed this slight lightening of color. Additional to this my blue green chromis was swimming around the tank at a huge speed yesterday and is now not wanting to come out from a hiding spot under the live rock.

I'm concerned that I'm about to lose both of them. I've done all the parameter checks and everything is consistant with where it has been and normal recommended levels and nothing has changed in the tank.

These are the only two fish in a 55g tank.

Any advice would be appreciated.

Thanks for the quick responses. I've been keeping an eye on the clown fish for the last couple of hours and she seems to be swimming around a lot more. In that it is 1am here I wont get anything much done tonight, and with her looking a bit happier I would like to get some sleep.

At present there are only the two fish in the tank.

I will do a water change first thing in the morning; normally I do 10 litres a week as that is the size of the storage tank on my RO unit. I do have a hydrometer for testing salinity (2 of them actually [and different brands] that both agree on the SG).

I've got about 18kg of LR in the tank and a skimmer.

Re pictures, I don't have any decent ones, and the only reason I noticed she is pale is because I spend too much time looking at her, it is a very subtle variation in shade and would be unlikely to show up in photos.

The tank has a fairly high phosphate level because of the local water supply (it is sourced from a river in a farming area) and I don't yet have a DI unit to complete the filtration, but my understanding is this is not a problem for the fish. Nitrate levels are higher than I would like, but are under 10ppm (after r/o i get 5-7ppm out of the tap).

There minimal algae in the tank, but due to the high phosphates and the LFS leading me down the garden path when i bought the tank (i ended up with a tank i can't have appropriate lights on) if i'm not careful it can get ugly.

The fish get fed on a variety of foods, mainly "Aquasonic Complete", "TetraMarine Marine Flakes" and freeze dried krill. the clown seems to like the flakes, the chromis prefers the krill.

Once again, thanks for the offers of advice; and snailrider, thanks for the welcome, although I have been hiding in the chatroom a lot

I'm thinking maybe I just woke them up last night. I haven't done a water change yet (one isn't due) but both fish seem happy today. I think I'm just expecting the fish to be active for too many hours a day. I'll keep monitoring them and see how they go.

hey toast, generally i'm using daylight with some artificial light in the evenings.... but it's all sorted now, i think i interrupted their rest patterns....

thanks for the advice, i was just panicing