Desperate Need Of Advice Due To Sudden Loss Of Live Stock.

For reasons unknown to me I have suddenly started losing fish and I am unsure what I should now do.
Tank is a Red sea 425XL
Firstly my most recent test results on the 2nd of March prior to a 70L water change
Salinity 1.025
Temperature 25
Phosphate 0.015
Nitrate 1
Nitrite 0.01
Ammonia Trace
PH 8.15
Alk 9.6
Calcium 460
Magnesium 1350

My current stock is now only a foxface, A single female clown fish and a bi colour blenny.
As for corals mostly softies, green, star mushrooms etc. Also have a gonipora, 2 small hammer corals, 1 torch, Acan and a Trachyphyllia

So my first loss was about 1 month ago, My royal Gramma had just gone missing without any explanation. I was gutted but I did at the time just put this down to misfortune.

Then about 2 weeks later I noticed that my female clown fish was being particularly mean to the male, nothing to unusual but he had a small about of fin damage so I posted to ask if there was anything I can treat the tank with to help him. The next day I noticed he was not eating which was very unusual. By the following day which was the 23rd of February he had died. I assumed the female had killed him. I had had them as a pair for 5 years and I was devastated he had died.

I spoke to my LFS regarding some advice and then realised that my Alk was low, it was 6.7. I did also pick up some treatment for the tank to help elevate stress which I have not used as I wanted to get my ALk up and stable first so I started dosing. In prior test the ALK was usually around 9.3 and perhaps the recent additions of coral had caused it to gradually drop.

I did stick to the maximum amount per day to increase gradually but I wish I had done this as several smaller does throughout the day but I did not realise and feel very foolish for this error. By the 28th my ALk was 9.3.

I was keen to get another male clownfish quickly as I was worried about the female taking out aggression on my carpenters wrasse.

So I added a young clownfish on the 28th. He settled in immediately and was swimming side by side with the female (more so than the other male ever did who kept to the corners of the tank)
I also added a Royal Gramma to replace my missing one.

I continued dosing Alk for a gradual increase.

By the 3rd of March my ALK was 11.2, Later that afternoon I found the new clownfish dead, without any visible signs why.
In distress I moved around rockwork hoping to find the gramma who had been hiding since purchase with the odd rare sighting which at the time I was not too worried about as that can be in its nature.
However with no signs of him I concluded he must also be dead.

Due to my poor judgment of moving rocks around my wrasse then took to hiding, I was keeping a close eye on him and say him yesterday (4th) he was feeding and although not swimming freely it looked like he was coming out of hiding and getting bolder. there was no apparent lose of colour and he looked well
I was confident by today he would be swimming freely. Not the case, I found his remains this afternoon. (5th)

My Alk has been maintained at 11.2 via daily dosing.

I have a 100L waterchange warming up ready for tomorrow.

What could have caused my sudden loss of fish.
I feel so guilty that it has been my fault with the dosing. But that does not really add up with the first royal gramma and male clown.
I have not added any Live rock for a long time but I did wonder could there be anything in the rockwork causing harm? but then would I have found the second male intact?

Really do not know what I should do next and it makes me feel like giving up. The last thing I want is for my tank to be a death trap. I had gone the 4 years or so with no losses and now this.

Any guidance would be very much appreciated

 

Thank you for your response, I say trace because I am not so good at telling with the colour with them being so minor. I make my own water (membrane changed September, filters changed in Jan, Di needs changing now.
Im pleased in a way that you don't think its the ALK, the self blame was awful. Although that would have been an easier fix.
I can run some test on the mix water tomorrow before I run the water change.

 

It might be worth getting an ICP test done just to be 100% sure there's nothing nasty in the water.

It sounds a bit like bad luck to me, these things happen, maybe if a fish died there was an unnoticed ammonia spike which stressed the fish enough to cause death over a few days. Ammonia tests are a bit unreliable at very low readings, they often do show a trace when there isn't any at all or at least extremely low, there always will be traces if you have fish. Nitrite is not harmful in salt water so 0.1 is perfectly OK

Why don't you join up at www.saltybox.co.uk it's the new forum to replace this one, you'll get more help there

 

Just a little update, LFS also did a water test for me, all came back fine. I have been treating the tank with medic but my Foxface has now deteriorated. He is behaving very erratically. I will set up a hospital tank tomorrow and my remaining fish will go in there for a period of 3 months. If they make it that long.