conifers do NOT need fertilizer.. unless a soil test indicates something is lacking... and the success of the others.. probably means nothing is lacking... water deeply.. and infrequently ... and insure that no bamboo returns ... and step away ... they will take a few years to catch up .. but they can do it on their own ... TOO MUCH LOVE CAN BE WORSE THAN TOO LITTLE.. WHEN IT COMES TO CONIFERS ken

Lovely pot!! To some degree, what you choose will depend on what shape you want - tall and rigid, tall and flowing, short and round, short and weeping, etc. My two favorite choices would be: Spirea Ogon AKA mellow yellow, which is fountain shaped rather than the rounded or bun shape of many spireas. White flowers, fine willowy yellow to chartreuse summer foliage, and red-gold fall color. Clematis Stolwijk Gold, which has gold to chartreuse leaves and early blue flowers. Grown on a medium trellis I think this would look stunning. Ninebark I think will be too big for the pot based on my P. coppertina. I'm personally not a fan of privet and IME they get pretty huge also. Some other thoughts: Yellow oak leaf hydrangea, Little Honey, though it has a reputation for being a bit fussy. It likes at least part shade Yellow-variegated shrub dogwoods (Cornus), though they might be too large Yellow elderberries (Sambucus) might stay small enough in your pot though they get large in the ground Clumping bamboos, though I am not sure if any of the yellowish ones will be hardy enough for you. Yellow leaved evergreens, such as some of the Chamaecyparis, would have foliage year round if you will be leaving the pot outside. Some heathers have yellow to gold to orange foliage depending on the time of year and the variety. Caryopteris such as Sunshine Blue have gold foliage and late season blue flowers. You'd need to check if the flowers coordinated with the pot. Gold grasses, either variegated like some of the Miscanthus, or solid like gold Hakone grass. You might also want to consider a water garden in your pot with papyrus, though it wouldn't be hardy or yellow. Here is a link that might be useful:

Can only prune back to parts with live foliage on them. Any sprouting from bare areas (right behind foliage) that may occur will be tot minimal to fill in quickly.

the needles probably died when you noticed the color change.. they just browned after winter sucked all the moisture out .... so the insult was last summer ... or prior .... a few inches of growth sounds right for the first year in transplant .. but the second year.. perhaps it should have been growing a bit stronger ..... which leads me to think there might be some soil issue that needs to be addressed .... contact you local soil conservation office .. and ask their thoughts about such .... perhaps your soil is way out of whack for such .... also .. you don't mention your soil .... too wet is never good for most conifers ... is there a drainage issue? ken