This may not be applicable to the first one, with the browning leaves, but here's what happened to one of mine this year. I bought two clems and sank the pots in the garden, as I always do with new ones, side by side. A week or so later, one is doing great, growing and blooming its head off and the other has been reduced to a twig. I figured out that the slugs were eating one and leaving the other alone, so I pulled up the twig in its pot, and moved it pot and all to the driveway during the day to get sun, and brought that danged thing inside every night to keep it from the slugs. Several weeks later, after it had put up TWO stems and had grown about 2' tall, I moved it back to the garden but in another place, and darned if the slugs didn't attack it again, but not the ones next to it. I have gone out in the dark several nights since and killed the slugs feeding on it, but I don't know how I'm going to protect it when it gets to its permanent home, and I don't know why slugs like that particular one better than any of the 60 or so others I grow.
Now, as a general rule, clematis likes a lot of water - are you sure you're giving yours enough? And, don't give up on them yet. I find that clematis is the one plant I grow that is most likely to come back from the "dead" if you pretend it is still there and keep watering.

Though I don't know the size or condition of the plant(s) you received, a couple of points that might be helpful:

(1) If your plants are small, they could benefit from a year in a cold frame or, failing that, being babied in the spot you've chosen (well-prepared hole--plant a good two inches down from the soil line; untangle and splay out the roots--some mulch and protection from full sun for a while.

(2) I suspect your plants went into full sun too soon, without a hardening off period. Give them some good shade, gradually allowing the sun to shine on them, as they move into winter. All the water in the world won't help a plant that's thrust into full sun too soon, after growing under lights perhaps, then weathering a trip in a box with total darkness.

Gary

I never have much good to say about mail order Clematis. They have always come to me wimpy and in need of a years babying. however, the plants I buy at the local stores, on sale, end of season do wonderfully! They have been watered all summer, given attention, out of bug harms way. they are just waiting for a real garden. Starting with plants that are ready to establish and grow, not ready to perish when you breathe on then wrong, is the key to success until you want to fuss for a year on a plant that isn't delivering.