Brown spots that turn Yellow

[KeepinItGreen]

Hey all, This is my first grow I am growing in a closet type setup with a 400W mh light and plenty of airflow.
I have 4 NL fem. that I'm growing in Foxfarm organic planting mix. I started the plants in peat moss potts with jiffy mix, and once sprouted I had them under some cheap floros, and once they had about 2 sets of leaves I transplanted them into 3gal grow bags with the organic soil.
When I put them in the 3 gal grow bags i turned on my 400w mh and burned the plants. I moved the light all the way up and the plants started to recover and now at about 4weeks in they are about 5" tall with alot of leaves.
The problem I'm having can be seen in the pictures but there are brown spots forming on the middle of some of the leaves and they later turn yellow.

I'm using
Foxfarm Organic Potting Mix
Filtered tapwater with a ph of 6.7
Foxfarm POM tomato/veg. Organic fert
400w mh
humidity 20-45%
Temp. 70-80F

 

[KeepinItGreen]

Hey all, This is my first grow I am growing in a closet type setup with a 400W mh light and plenty of airflow.
I have 4 NL fem. that I'm growing in Foxfarm organic planting mix. I started the plants in peat moss potts with jiffy mix, and once sprouted I had them under some cheap floros, and once they had about 2 sets of leaves I transplanted them into 3gal grow bags with the organic soil.
When I put them in the 3 gal grow bags i turned on my 400w mh and burned the plants. I moved the light all the way up and the plants started to recover and now at about 4weeks in they are about 5" tall with alot of leaves.
The problem I'm having can be seen in the pictures but there are brown spots forming on the middle of some of the leaves and they later turn yellow.

I'm using
Foxfarm Organic Potting Mix
Filtered tapwater with a ph of 6.7
Foxfarm POM tomato/veg. Organic fert
400w mh
humidity 20-45%
Temp. 70-80F

I was also wondering if they look small to you guys

 

[amsterdam_goodies]

I was also wondering if they look small to you guys

I am not an expert, but I think that you might be overwatering

 

[KeepinItGreen]

I am not an expert, but I think that you might be overwatering

I mist the cabinet alot to keep humidity up, So I havn't watered them a whole lot. I'm having trouble keeping my Humidity above 20%. Could this be the problem?
Any Insight from an experienced gardener would be greatly appreciated, I am started to get a little concerned if the plants are have problems at a month in.

 

[KeepinItGreen]

I mist the cabinet alot to keep humidity up, So I havn't watered them a whole lot. I'm having trouble keeping my Humidity above 20%. Could this be the problem?
Any Insight from an experienced gardener would be greatly appreciated, I am started to get a little concerned if the plants are have problems at a month in.

Anybody have any Input?

 

[amsterdam_goodies]

no i doubt its the humidity... highly doubt it... you said u mist them, it could be a burn from water residue on the plant. water can sometimes become magnified by the intensity of the light and put spots on leaf...

 

[amsterdam_goodies]

i dont know that its that though to be honest

 

[1kooguy]

You should've added more perlite ,and garden lime to the mix:http://www.gardeners.com/Garden-Lime/FlowerGardening_FertilizersSoil,35-738,default,cp.html. Water when the bag is not heavy,check the weight when its watered,and when its dry.Add a few drops of hydrogen peroxide per liter of water.If your going organic,you need to let the water sit,or buy something thats gets rid of the chlorine.