A few brown dots in vegetative growth cycle

[McWoggy]

Indoor/Outdoor: Indoor
Growing Medium:Coco
Growing Style:Hydroponics
Watering/Feeding Frequency:Every 2-4 Days when pot is extremely light to lift
Nutrient Strength (PPM/EC): Lower than required (No other way to say it)
PH Levels: 5.3-5.7 at feeding time
Temperature/Humidity Levels: Temp is 24-28ºC/ HUmidity unknown

Air Flow/Fans etc.: passive intake with centrifugal exhaust air flows though cool tube and out a carbon filter
Lighting Type (CFL/HPS/MH etc.): HPS
Total Wattage: 400W
Growth Stage: Veg
Plants Age: 6 weeks
Cannabis Strain: indica dominant cross

 

Today one of my cannabis plants looks like it has a nutrient deficiency. I have previously had yellowing of the leaves on this plant so I add a little calcium and magnesium to every feed and the yellowing has not returned. At first glance of the plants leaves I thought I had spilt a light brown substance on the leaves and I tried to wipe the blades of the leaves clean. The small dots did not rub from the blades of the leaves. After a more thorough inspection there were a few more affected leaves that had the same browning, only it was around the margins of the blades of the leaves.

So I have a healthy green plant that has 10-15 leaves with brown marks appearing. A few blades have 1-5 small dots and the others have a browning around the margins of the blades of the leaves.

I can only think of calcium manganese or something else is lacking. I have never seen this occur from nutrient burn but I am not ruling it out.

I cannot take any photos for another 1-2 hours but I wanted to ask someone in these forums in the meantime just in case someone had an idea from reading this.

[fuzzimuzzi]

Could the light be to close?

Did you spray water on the leaves? 

[louise]

Photos are what's needed McWoggy, clear, well focused photos.

[buzzo]

P.H. is too low to start with.

More than likely Fungus Gnats chewing on ya roots,

But like Lou says Photos are needed