How big are these plants, and what size pots were they in?

Some yellowing and dying of lowest fan leaves is normal, especially in maturing and tall plants.


That curling could also be wilting from the leaves being too close to the light or too much humidity/not enough ventilation, too.

When you replanted them, what did their root balls look like? Were they full and bushy, or sparse? Were there visible root hairs throughout the soil? If you pull a plant with healthy roots out of the proper size or smaller pot, it will take all the dirt and the rocks from the bottom with it. If the plant did not have a healthy root system, chances are it will tear free of the dirt. Did your roots look like they could support all the dirt, or did they look like they'd probably tear free?

Sheist is right about overwatering. But I think too often overwatering problems are actually UNDERDRAINING problems. It amounts to the same sort of problem, but underdraining can occur whenever the contanier can sit in a puddle of water, and regardless of how conservative you are with watering. It's all in the way you prepare your growing container and choose your dirt. I'd not be choosing pearlite, especailly if I suspected soil problems.

I'm not snobby enough to pretend I can manufacture good dirt at tru-valu prices. I use a premium potting soil, especially to start my plants. Back Gold and Miracle Gro are both ok. They're sterile, good ph, low ratio of fillers, and drain well. I lay down a good layer of gravel in the bottom of the pot -- 3 inches in a 12" pot -- and then add dirt. I pull off those silly little saucers that so many pots have stuck to their bottoms, and put the saucerless pots in those foil turkey pans you can get at the supermarket at 3/$2. Then I'm assured that what run in will either be used or will run out and away from the soil, and that if it runs out it will be under control in the grow room.

I let my plants tell me when they need water. The lower leaves will wilt. When you get good at noticing the difference between a wilting leaf and one that's just taking a nap (they do that), you will never wonder if you're overwatering. In the middle of a hot summer, in the pre-bloom fast-veg period, they may need water daily. In the cold winter, during the bud-finishing period, they might only take water weekly.

I keep my plants on the dry side. I believe it encourages good root development and discourages mould and rot. But when I water, I give them a good soaking. It flushes out stangant nutrients and salts, and draws oxygen down deep into the soil. The results are really deep green, plump-looking plants that exhude a happy fragrance and produce happy buds, and root systems that I have to beat the dirt out of when I recycle them.