I see you're new and probably unfamiliar with how the forum works. Usually, it's better to start a new thread, than to try to get your questions answered on a thread that isn't related to your questions. You would do that by going to the appropriate forum and scrolling down the list of topics (threads) to the box at the bottom, where you can create your own topic/thread and ask your question. You're pushing the zone very hard by even planting 'Tonto' in your zone. Listed as a zone 7 plant at the coldest, it's likely it wouldn't make it through a hard winter in your location, though mulching heavily can offer some help in protecting roots. The plant needs a cold rest period (dormancy) to perform well in the subsequent growth cycle, so over-wintering indoors is decidedly less than a good choice. If you decide to go ahead and plant, I would probably keep it outdoors until it goes dormant. Bring it into an unheated garage or bury the entire container against the north side of a heated building until danger of hard freezes has passed, then plant out in a protected spot, if possible. Make sure you monitor its water needs and take steps to prevent the soil from drying completely over winter. Al

I don't think I've seen so many brown spots on my clematis before this year. We did have lots of rain this spring. I also noticed some of my clematis like Jackmanii and Julia Correvon are smaller this year. Katie

any chance of pictures? Sure would help us help you!

Might one be against a wall or other situation where there might be a chunk of concrete under it like a footing? Might the soil beneat the stunted one be more compacted or its drainage be too good, allowing the water to drain through more quickly than the well grown one? Might the stunted one get more reflected/radiated heat from a wall, fence, sidewalk or patio, etc.? As has been stated, there are many possibilities, requiring a better understanding of the actual site to provide accurate diagnosis.