i need experts, 3 grower m8's cant help - can anyone ?

got 250 hps, with mixed spectrum red +blue, xtractor, filter, temp is 26, in small cupboard, got 3 plants in nft system, but have already done couple in soil, and they all had veiny leaves, then died ?? got 3 growers scratching there heads as it keeps happening even in different mediums

check the things that were the same each time they died
same ec pen?
same ph pen?
same nuts ?
check , test , these things for falts.
thats the only thing i can surgest with out being their,
sabertarge?
hope that helped not hindad

may be try sum diffrent nutes.. or just lightn up on them..