Charleen,
I think you may be dealing with three possibilities here.
1) Different varieties of sempervivum have different levels of vigor. The semps on top could be not as vigorous as the ones on the side.
2) Water movement in soil is governed by a number of forces, one of which is gravity. It may be that you are getting more moisture to be retained by the bottom of the strawberry jar, being that it is lower but also because it is closer to the ground/wood (which would retain and buffer moisture). Note that the semps on the top of the jar have some dried leaves around the crown of the plant. This could mean that these plants have been drying out more than the ones on the side which are lower and more protected. Sempervivum will sacrifice lower leave to keep the upper portion of the plant growing/alive when too dry. It's easy to spot this kind of behavior. For example, if you receive a package of bare root sempervivum, some will have dried leaves at the base of the plant, from having conserved water. You can demonstrate this behavior by just digging up a hen and leaving sit in the open unplanted for a few days and watching it.
3) With all of the other pots around, the base of the pot is probably getting more indirect light than direct sun. The conditions for the plants at the top may not be appropriate for the variety growing there, especially if they are getting a lot of sun in a hot climate.
I suggest you try watering (this container) more frequently, but with less water. This should stimulate the top plants more without drowning the bottom ones. You may also want to consider replacing the top semps with some that are more vigorous or a bit more shade for the top of the pot.
I always seem to have a few semps that are just not happy with their environment. Some will respond well to being moved to another location and others are just more demanding. ( I'm just thankful I didn't decide to collect orchids.
) With a little TLC and some patience, I can usually figure out what the fussy ones want.
