Dropping Like Flies =[

[xamy_valox]

Hi there, I have posted about this before but never really got an answer, not sure if that is because there isnt one!
Basically over the past couple of months I have been loosing fish quite rapidly compared to my previous tanks.
Today I appear to have lost a neon as I cannot find it anywhere in my tank, so I'm assuming it has died and been eaten by the other fish in the tank (though I've never had this happen before) and a few days ago I lost a cherry barb.
Other than one of my neons being incredibly fat (cannot seem to shrink him down) my fish seem to be in good health, lots of movement, eating fine, no bullying since I lost my rams.
The harlequins, neons (apart from one) and the 1 cherry barb I have lost have been from my very first tank (a Fluval edge) which I had roughly 2 and a half years ago. Do you think I could be losing them due to old age?
My tank stats are fine, 0 ammonia, 0 nitrites and 5 Nitrates (I may have got them confused, I always do despite making a rhyme in my head haha).
I feed every other day and have up until this week been doing weekly water changes of about 30%.
The tank temp is at 26/27 degrees an heavily planted with lots of hiding places (coconut cave, bogwood).
I just don't get it =[
xx

 

[pablothebetta]

What size is the tank and what is the full stocking list? Sure there are no diseases and that nothing has got into the water?

 

[xamy_valox]

125 litre tank with:
3 Harlequin Rasboras
4 Neon Tetras
4 Platinum Tetras
5 Cherry Barbs
7 Corydoras
1 baby Angel fish (going to a new home once I find a decent one)

I have no idea how to see if there are any diseases in the tank, but visually all the fish look fine. No signs of ich, velvet, or anything on the skin.
Poop looks normal and as said previously they are all eating fine.
Haven't added anything to the tank for at least a month, maybe even longer. I can't even remember the last thing I added!
xx