Understanding hardness

Got home today to find my male apistogramma dead on the bottom of the tank not a mark on him so went about usual process of testing water.

pH - 6.8
Ammonia - 0
Nitrate - 0
Nitrite - 0

Have just invested in a hardness test kit so i gave it a go

GH - 500 mg/l
KH - 40 mg/l

Now according to the little booklet these are way off from anything normal which has got me worried, have already got peat in the filter and there has been almond leaves in the tank which i thought would've softened the water enough. Can anyone explain these readings to me? and any tips on getting the water to discus conditions. Thank you.

Tapwater is coming out at

GH - 120 ml/L
KH - 50 ml/L

now dont take my word for this but does bog wood soften your water and sorry to hear about the fish

A wouldnt of thought you would have any problem with hard water in Darlo. Its usually down the coast hartlepool, easington district where the water is hard. Sorry to hear about the fish mate.

Well have been playing around again with two ph buffers, one from waterlife and one from seachem.
The waterlife one holds the ph spot on and the gh is less than 20 mg/L but the kh is through the roof. Whereas the seachem is a bit trickier to get the right ph but the gh and the kh is holding the same as the tapwater. Can anyone tell me what sort of readings i should be getting? as this is really confusing me now.