Dark to light green, rust spots (pics)

Here's my description of the problem. Pictures below.

First this plant is about 3 weeks into flowering. I first noticed the outter edges of the leafs were a light green with the centers being darker. Now I see some rust spots starting to develop on a few leafs and signs of slight burning. I'm thinking it's one of three things.

1. Nute burn. I just recently gave them ~1000ppm GH floranova bloom.
2. Nitrogen def. The rust spots worry me though.
3. K def. I don't understand why this would be because I'm using bloom ferts and the rust spots didn't appear until after the last feeding.

The next watering will be with Cal/Mag+ and R.O. Water only. Bloom nutes added every third watering or so and Cal/Mag+ the watering after. Water PH is 6.0 with nutes and 7.0 without. The smaller plant next to it doesn't share any of the symptoms of the larger plant. This plant is directly under the HPS and does get warmer then it's smaller sister, but doesn't show signs of heat stress. Temps in the high 70s - low 80s.

bump, no ideas huh?

IS there anything you did differently? Just the concentration of nutes is different? How much was it originally?

In the grow faq this looks similar, says potassium toxicity.

http://www.drugs-forum.com/growfaq/97_files/nietz140.jpg

About two weeks ago they were given about 500ppm of floranova bloom. Then watered with cal/mag+ and RO water.

The light green/dark green coloring started before the last watering, but the rust spotting started after. It's been about 3-4 days from last watering with 1000ppm bloom.

phearless said:

IS there anything you did differently? Just the concentration of nutes is different? How much was it originally?

In the grow faq this looks similar, says potassium toxicity.

http://www.drugs-forum.com/growfaq/97_files/nietz140.jpg

Click to expand...

Here is potassium def.


Maybe I should just flush and see what happens. It's so hard to flush a 5 gallon bucket though.

I dunno, I would agree on flushing it and 'starting anew' from that. I don't have much experience but I hope that will make the difference, otherwise they are looking really good. I watered my plant with a very strong nute solution for the first time after 14 days (water before that) and got a tiny rust spot on one of the bottomest leaves (the first two that sprout after the round ones but it jsut stopped at that, dunno what it was. Now those two leaves are slowly withering I hope that's ok but the rest of the plant looks good check it out.

The pic taken a few mins ago, lights just went on day 21 snow white under 4 cfls just added the fourth today and transplanted yesterday to this bigger pot.

when flowering the fan leave will go lighter in colour den eventually turn yellow this is completely normal (only when flowering) the plant is using up all the nitrogen and other chemicals thats why they are changing colour perfectyle normal