Leaves become yellow under hps ?!

Hey mates I was growing under 150w cfl and soon I switvched to 400 hps but still 18/6. The last two pairs of leaves on my plant are a little yellowish and more thin than the previous. The lamp is 35cm or one foot far from the plants...
Also is there a chance the preflowers to look like male the first few days and than to produce pistils??

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Originally Posted by burzuming

Hey mates I was growing under 150w cfl and soon I switvched to 400 hps but still 18/6. The last two pairs of leaves on my plant are a little yellowish and more thin than the previous. The lamp is 35cm or one foot far from the plants...
Also is there a chance the preflowers to look like male the first few days and than to produce pistils??

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I think they look similar in early stages

yellowish could be a nute problem

Usually when there are not enough nutrients the lower leaves become yellow. Now only the new ones are(which grew under the hps) Im fed it with nitrogen and iron 5 days ago so that isnt the problem. Havent experienced yellowish leaves under hps?

If the leaves are turning yellow around the edges and curling then it could be that the hps is a little too close. To get the right distance move the light so that you can hold your hand at the top of the plant for a minute before it gets too hot. Then move it up another 2 inches from that distance and you should be set. Just continue to keep the light that total distance away from the plant as it grows.