local marine fish store extremely high kh

[PT7455]

hi, I am a new user, 5 years saltwater tank experience, still young

the lfs store that I visit every week, I test the store water, the kh in api test kit needs 33 drops to change colour, red sea test kit need 3 time full injection to change color, and I see the ph meter in the store is 8.8 wow!!, and I test the water use my pin point ph meter is also 8.6 high!!!!!

why all marine fishes in this store are looking healthy in such high kh? and high ph? some fish I visit every time still alive and swimming there in a month?
do u think the owner has add something in the water make this so customers keeps coming back, well the price is lot cheaper than other lfs

now the question is, I ask some customers the same questions, their fish die in 3 days or in a week when bring it home, just like me every week, is that kh make those fishes can't live in our home tank in normal water?

kh 10, no3 5/ nh3 0/ pho 0.25/ mag 1200/ ca 340/ sg 1.023/ ph 8.1

all my old fishes in my tank lives 2 years and so healthy and fat, eats like pig,
but all new fish die in few days

all new fish has been slow using drip at least 1 day before add into tank, all old healthy fishes catched and moved in the sump for no fight to stress