Leaves dryng getting yellow and dying

Man my leaves start normal, them the older leaves from the bottom start getting yellow in the tip, and them start to dry out by the tip and them the leave dry out and die,can anybody help me

 

What sort of soil are they in ?

 

what light period are they in?

 

this is happenening to me kind of too... sometimes the points of them are white and sometimes not, the plant seems to be leaning right now, its under a 400w light its in good soil im sure of that, the plant is a little over a foot in its 1st stage 24hour light

 

How old are the plants and what are you feeding them?

 

plants are prob 3-4 weeks about a foot high so far just watering them its still growing fine, just not all green