Clematis wilt - or something else?

[TheCyclingProgrammer]

Our Clematis Cartmanii "Avalance" which was planted last Autumn has suddenly taken a turn for the worse. It hasn't even flowered yet.

Is this Clematis wilt or could it be caused by something else? I forgot to feed and mulch it in March - I've applied some blood, fish and bone, given it a good drink and mulched around it with rotted manure but I guess if it's wilt that won't help and I'll have to cut out all of the infected shoots.

Some of the healthy looking bits:
https://www.icloud.com/sharedalbum/#...C-439F7121B217

Browning leafs and dying flower buds:
https://www.icloud.com/sharedalbum/#...4-8AD6E4038EE6

Black leaves lower down:
https://www.icloud.com/sharedalbum/#...4-72E14B7992D9

Close-up:
https://www.icloud.com/sharedalbum/#...7-E99F8501C2B0

[nickdub]

Not seen Clematis wilt, so I'm just not sure on that.

One other thing to check for is damage where the stem enters the ground - sometimes slugs will get desperate and eat the outsides off the stem at ground level leading to the death of everything higher up. Just push back a bit of dirt with your finger and it should be obvious if anything has been eaten away or not.