I'd transplant asap and start them on 1/2 strength flower nutes.

What part of the plant is yellowing with blotches? (lower fans, all lower leaves, up to mid-level fans...) Effective light from a 400w is about 3 feet, so yellowing down that far is normal. If not the lights, it might be calcium deficient, and adding 1 tsp of unsulphered molasses to each gallon of properly ph'd water will cure the calcium defeciency, and Molasses bulks the plants up. (don't overuse) Most bud swelling products I've seen are some form of molasses recipes.
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Your ph might be off, locking-out nutrients. Sometimes you can call a local aquarium store and they can let you know the ph of local tapwater. If not, they sell freshwater aquarium test kits for $7.00 or so. By knowing the ingoing ph of your water, you can identify if it's the cause of the problem, or eliminate it from possibility.

If replacing soil during a transplant, and you're using MG potting soil, you'll have to adjust nutes accordingly. (ease-up on the flower nutes to perhaps half-strength...but watch results and adjust as needed) The plants will have another bout of stretching as the nitrogen is gobbled-up. But since you're only adding what...a gallon of soil to fill the new pot, not a big deal, however you might need to watch headroom.

Generally, if you restrict the roots, you are restricting canopy growth, too.

Plants will start to suffer if you do not restrict nitrogen in flower. A little is necessary, but too much is damaging. get the bloom nutes first and foremost.

Summary, and an educated guess sans photo's: rootbound and starved for bloom nutes. Would suck to get this far, and be screwed over a $10.00 bottle of nutrients.
Rusty Trichome Reviewed by Rusty Trichome on . No Pic, But advise is greatly needed/Appreciated. almost 4 weeks Flower Okay, Let me start this out by saying this. I have no camera to take any pictures so sorry that is out of the question. Little Beak down I guess I am using Mg time released soil/ Really ain't any nutes left in the soil Imo. I have a 400w Mh in a Ac hood. Have a fan pulling air threw the hood from out the box. I have not got my area dialed in and finished like i want but this has been working so far. My hood is about 6-7 inches above my Rating: 5