Issue with lemon jakes

[JraGold]

So I bought 8 lemon jakes 1 1/2" from a fairly reputable store in my area last thursday. Get them home, acclimate them slowly and put them in my 40 gallon which has 2 red top lwandas roughly same size in it. Wake up the next day to find I lost a lemon jake. It was the biggest of the group. Next day I wake up to another dead lemon jake. Second biggest of the group. Pretty pissed at this point I email the seller and he says he's gonna reimburse me for the 2 fish.
Almost a week later I find yet another dead lemon jake today. Third biggest of the group. What gives?
My parameters are spot on. The tank has been up and running for 8 months or so.
Any ideas? Or suggestions?

 

[TheCommunityCichlid]

Any bullies or anything out of the ordinary? That tank will work for now but is far to small in the long run too.

 

[JraGold]

I haven't seen any aggression at all. Ya I know re tank size. Just using it as a grow tank for now.

 

[Andrew McFadden]

What are the water perimeters? They should be fine aggression wise at that size. Most peacocks don't show a lot of aggression till they are bigger

 

[JraGold]

Ammonia 0
Trites 0
Trates 10
Ph 7.8