too much water? rich soil?

Here is a link that might be useful: topical link

Ceanothus should be planted in Fall not Spring.

I can't see your picture, but deep watering was good, though usually that's done right after planting. You might be seeing some stress from that first week. Ceanothus are tough, in my experience, just make sure you have a good watering basin, add some mulch (shredded redwood AKA "gorilla hair" is the best). Check under your mulch for signs of dryness and water as needed. You should be fine.

I thought I'd check back in here a year later. In the end I think it turned out to be overwatering and not well-drained soil. After this photo I did one more deep watering, one of my Ceanothus died (the one pictured), and the other one came back and is growing vigorously.

I planted a new one in the fall/winter to replace the dead one, and this time I added some small gravel to help drain the soil. I also didn't water since the soil was already somewhat moist from the winter, and I believe it gets some moisture from a nearby grass area that is watered regularly. I haven't watered either of them and they are both doing great.

The one that survived from last year has grown probably two feet and gave an awesome display of dark blue blooms last month. What a beautiful plant/tree!

Here's the photo from my original post, the one that died (RIP):

i did something similar with my ceanothus concha. i did amend my soil because i had strait-up clay plus construction fill, so just making it normal took a massive amount of compost. i planted in june because it's when i could and because i live smack in the area ceanothus grow wild. anyway, knowing they hate water i planted and gave a moderate watering. a week later i gave a light watering. next week, they yellowed. a week later, figuring i hadn't really given much water, i gave another light watering. more yellow, plus fallen leaves. finally i threw up my hands and said, "you're on your own." leaves continued to drop but i just wait it out, and two months later, both have completely recovered and put on new shoots. i transplanted one today and when i was done packing the soil down my boyfriend said, "don't you want to water it?" and i gave a resolute, "no." and no matter what it does while it adjusts, i will not ever water it again. my soil is good and holds moisture well, and autumn is right around the corner.

For those of you planting Ceanothus, DO NOT amend the soil with compost or any other nutrient. Ceanothus are genetically-designed to live in nutrient-poor soil. They get their nutrients by forming symbiotic relationships with frankia bacteria in the soil. Frankia attach to the roots and provide the lilac with nutrients, water, and protection from pathogens. The bacteria get carbohydrates in return. Adding nutrients causes the Ceanothus to drop the fankia from its roots and leaves the plant open to attack from pathogens. You can establish a good frankia population in your soil by mulching heavily with pine, fir, redwood, or oak bark (chips or shredded).

If you have poorly-draining soil, amending the soil with rocks or sand will usually create a mess. Keep in mind that water will drain via the path of least resistance. If you have thick clay surrounding a heavily-amended spot, water will drain into your amended area and your plant will end up living in a bathtub. (Also, mixing sand and clay will form a concrete-like substance that won't drain.) At minimum, you would have to amend a very large area (like 6' x 6' x 2' deep), as plant roots tend not to travel from one type of soil into another. And even then, getting it to drain well will be tough. If you have clay soil, select a Ceanothus that will tolerate clay and plant in a sunny spot with the crown of the Ceanothus 1/2" above ground level. If you mulch a couple of times a year, the mulch will naturally break up the clay and improve drainage.

Water lavishly upon planting and perhaps once a month for during the first summer (water around the perimeter of the root ball, try to keep the crown dry). They'll do best on natural rainfall afterwards. If you're in a bad drought year, give the Ceanothus a couple of extra waterings in the late winter/early spring.