Yellowing leaves in Jade plant Crassula tetragona
I grew these from cuttings I got in January, and they rooted and grew great until May. Now leaves turn pale or yellow-green and drop. The yellowing doesn't seem to produce any kind of pattern, and it isn't happening in any specific area of the small plants. The leaves lighten or turn a yellowish-green, then fall off. It happens to older leaves near the bottom, and to leaves about the middle of the plants, and it's even lost a couple tiny leaves on new branches.
Potting mix is a well-draining succulent mix. Pot is 4 inch-wide, roughly 5-6 inch-deep plastic type with good drain holes. The bottom half of the pot is filled with broken stones for good drainage, so there's only a few inches of soil. I rooted them in this same pot and soil in January/February, and they did great. I'm in very shady woods on the north side of a hill in western Oregon, so I put them in a south-facing window where it was quite dark except for about 2 hours of direct sun.
They rooted; the leaves became turgid, and they grew fast and started branching like crazy. The branches are very thin, but they're also very new, and the leaves aren't spaced too far. Once the Oregon rain stopped for the season, I moved them outside into the sun in the same pot. The sun was higher by then, so they got less shade from the hill. I thought they'd be happy, but the first thing I noticed was a pair of leaves that appeared to have shriveled and dried up. I thought it might've been too hot there so I moved them slightly to get partial shade, but it's getting.g worse.
I let the soils get mostly dry between good waterings, but for fear I'd over-watered them, I de-poted them to check the roots. They have so few roots I don't know how they survive, but the roofs are not soft, broken, or rotten. There just aren't a lot of them.
What heck am I doing wrong?
I don't know if it makes a difference, but C. tetragona isn't at all like most spoon-leaves jaded. It's leaves are small, pointed, and narrower than a pencil.