small problem with outdoor plants

plants range from 1 week to 3 weeks into bud and there all showing the same signs of bottom leafs yellowing then turning whiteish and dieing off im thinking its a mag def just wanted others opinion before i started giving more nitrogen
using biobuz grow and bloom in smart pots ph around 6.5 this just started this week on most of my plants fast ph might be an issue due to cheap ph meter but the soil also has lime in it so that shouldnt be the problem in thinking mag or n what do you guys think

Looks like N def to me, but a little more N in a watering and you should be good to go. Nice looking plants by the way.

thanks buddy started them from seed in april first one is pineapple express and the 2nd is Frisian dew

i got some fem pollen brewing up to hoping to cross the 2 nice fast flowering resilient plants just a little rusty haven't grown in awhile also first time using organics but loving it

Ya, those Smart Pots are on my list. If you use tap water mag may not be it. I would try some Miracle Grow Organic Bone Meal. I use it on my outdoor grow just before it rains. Really brings it up a notch with some tap water. Just sprinkle around the bottom with a spoon just enough to cover underneath the plant. About two spoon fulls usually does it.