It looks like you are overfertilizing and your pH is off. You should not be using a Grow fertilizer (the Iguana Juice) or ANY fertilizer with a high Nitrogen content during the flowering phase. You don't want much nitrogen during that phase, just a small amount. You can tell they are getting too much nitrogen because of how dark green they are this far into flowering. Also the top dark green leaves are showing the "downward claw", another sign of too much N. You need to stop using that fert and start using a Bloom fert. Your leaves look like a Phosphorous deficiency, which could be due to you not using a bloom fert and/or the pH being off.
How many weeks have you been at 12/12? Also how long does the strain take to finish, if you know? Your fan leaves should be naturally turning yellow, then brown, then falling off as the plant uses their energy to produce buds. Do not cut them off just because they look bad, the plant needs their energy and you should leave them until they fall off or come off with very gentle pulling.
You probably have a whole bunch of acid salts built up in your soil that need to be removed via a flush. You need to run at least 3X as much water as the amount of soil you have through to wash out the acid salts. So if you have a 3 gallon pot, you need to flush with 9 gallons of correctly pH'd water (6.5-6.8, err on the high side if you can't measure that precisely). If you have never flushed these plants since they have been in this soil, you might need to use even more water than that. You should test the pH of your runoff water (the water that comes out the drainholes) periodically during the flush to see if the pH is going up. The acid salts are mostly near the top of the soil so it could take a LOT of water to push them all the way down to the bottom and out the drainholes.
On the last gallon of your flush, add 1/2 str nutes since flushing will remove nutrients as well. Just don't add back any nutes with a high Nitrogen content, you need to start getting that N out of your plant before harvest time. If I were you I would use a final flush solution, like Final Phase or Clearex. These products have chealates which will bind to all the chemical ferts and wash them out of your plant. I just used it on my latest grow and I am very impressed with how clean tasting the smoke is. You want to use this about 7-10 days before you are going to harvest. If you're interested you can google about it for more info, and I can tell you how I applied it in dirt since the only instructions I could find were for hydro setups. Just let me know.
