Hey guys, I have 5 plants that are 5 weeks old in veg (24 hrs a day 1000w MH) in Fox Farm Ocean Forest Soil. 4 were topped about 2 weeks ago, and 1 was super cropped last night. I have been noticing some overall yellowing on the upper fan leaves which appear to be starting from the inside of the leaf towards the margins. On 1 plant there were "dead spots" on the margins of a couple fan leaves, but no other leaves. pH is at 6.6 (measured last night) and has been pretty stable there since day 1. I haven't fed them anything at all until last night. I gave them 5 mL of Heavy 16 Veg-B in about 2 gallons of water because I suspected a possible Mg/Fe/S deficiency. Based on these pictures, what does everyone think it could be? (They look very yellow in some of these pics due to my phone's camera not being able to adjust correctly).
Also, on one of the plants the leaves are contorting and curling in on the margins. I don't know the room temperature (dead battery on my gauge) but the light is about 3.5-4 feet above the canopy and it is not physically too warm for the plants after leaving my hand above the tops for 1 minute.
You have a minor Magnesium deficit on your plants... the brown spots are a minor calcium deficit waiting to happen. If you feel confident that your ladies have received the appropriate amount of micro's you'll be good to go. Next watering it would not hurt to add a teaspoon of epsom per gallon of water.