Please help. Leaves are curling down and some are turning yellow

[budlight89]

Hey guys,
first time grower here. I have been using a 6400K CFL propagation light, haven't given the plant any nutrients in the last few weeks, but as you can see, the lower leaves are starting to curl downwards. Also, the top leaves are turning yellow. Any advice or tips would be super appreciated.

 

[thedubside]

im new grower so prob best for more experienced growers to comment, but looks like zinc deficiency to me, for the discoloured tips. the twisting happened to me too, i thought it might have been a PH fluctuation that causes the twisting

 

[budlight89]

im new grower so prob best for more experienced growers to comment, but looks like zinc deficiency to me, for the discoloured tips. the twisting happened to me too, i thought it might have been a PH fluctuation that causes the twisting

Thank you