Identify this deficiency.

My WWxBB plant which was doing excellent suddenly started showing the following [refer to picture]

It's rusty looking, I inspected both sides of the leaf with a 60-100X loop and saw no bugs or anything to look like mold.

She is mixed in Sunshine#4 w/ perlite. I was giving her 2 tsp GB, 2 tablespoons BB, 1 tsp TB, 1 tsp calmag.

The PH of the water I give her is between 6.5-7.1. my tap comes in at 8.8. It runs through a brita filter.

The plant has been vegging for about 5 weeks in a 3.4 gallon airpot

My temperature is in the upper 70's lower 80's with with night temps going to 65. humidity is 45-55%.

The plants are in a secret jardin 120, 4x4x7 ft tent with a 600 watt digilux MH.

I'm not sure what the deal is, I have this and my tutankhamon showing this, it just started in the last day. I took off the bad leaves and the rest of the plant is fine. I then flushed with 6.5 ph water.

The deficiency is located in the middle of the plants, located on 3-4 leaves on each plant. more so on the WWxBB.


Any experienced growers that can help it would be much appreciated.

put the leaf on top of a flashlight so the light shines thru the leaf and you can see the inside. If there are holes in the top and bottom of the leaf and not the middle, it is a bug problem otherwise looks like a magnesium/Iron problem

We're confident that it's not Iron related, but fully agree with JoC's Magnesium suggestion. Mg deficiency can get especially brown & necrotic, as yours appear, when combined with some Phosphorus def. Alternatively, it could just be intense Mg def.