stunted growth on clematis.planted about a month ago

If it's still healthy, then I think the word has to be 'patience' I'm afraid!

Wonder if it was a bit pot bound. I tease the roots out since saw it done on TV. Although it is a bit early to know what the problem is, especially as growth is slowing down now in many plants. May just need to be patient - til Spring.
Good luck.

Stop feeding them now, its too late in the year for that - just keep them watered as its so dry at the moment. Start feeding again in spring, if you want to.

Savannah is a non-clinging clematis. So it probably just had stopped growing this year. After pruning it next spring, you will see it growing fine, I'm sure.