YELLOW LEAFS AND THEN CRISPY BROWN FALLING OFF

Hi guys, im a starter in growing i put 2 aotiflowers from green house ( super lemon haze and sweet mango) im at the 5th week from seedling and l suddenly i see leaf by leaf doing the same thing that means getting yellow half of it then next day all then other down brown and crispy. I dont know what to do? i need your help.
Bio bizz all mix
bio bizz blooo, grow, top max, heaven,root juice and activera and some little bud candy for the taste
14 l
250 HPS lamp
24-25 temperature and 40-42 %humidity
water before i water is tap water left 1 day with top open and redued ph to 6,5 with some lemon.
Need your help dont know what to do
 

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