This guy needs some help.
First, I'm concerned about the area circled in red. I can't really make out what it is, but it looks like some sort of pest eggs.
If you can, take a closer picture, and make sure it is in as good focus as possible.
Once we have figured out what those whitish particles are, and dealt with them, I would take all the plants out of the pot, strip off the old dead leaves at their base, and re-pot them all in a new pot.
Underneath the old dead bases of leaves, which are as thin and brittle as onion skin, there will be lots of little new roots. At the base of the stem will be the old root bundle. The roots are pretty fragile, and easily broken, so you have to be pretty careful with them.
An aloe which is happy will put out lots of little clones of itself from the roots. I see none of that here. The pot is way to big for the amount of plant matter there is, so large sections of the pot will have stagnant dirt.
Aloes are funny. When they are happy they grow like crazy. But, when they get unhappy they can stay unhappy for years. Both under-watering and over-watering are very possible for an aloe.
Aloes will also take full summer sun, but the old leaves formed indoors will sunburn. The new ones formed outdoors will almost have a reddish tint.
Plus, they don't seem to like peat based potting soil as well as other plants do.
Lets find out what stuff on that one plant is, and go from there.
This is what a fairly happy aloe looks like.