Need Help with a Greenhouse Grow

these sorry looking things are actually white widow.about 4 weeks old.the leaves have gone dry and are curling under around the edge of the leaf.now the veins are drying all the way up the leaf its looks like lots of letter v's going up the leaf .really stuck on this one lads...info.they had a bad start with wrong ph but thats sorted now...any ideas lads.bigbud 012.jpgbigbud 011.jpg
 
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