have not done a. polyphylla, but have grown several aloe species from seed. they are easy to germinate but be careful until they grow a real root system, as they can develop a few significant leaves and still have only a thread of a root system. I have had no trouble exposing them to air--they didn't need the plastic bag. I avoid any direct sun until the plants have some significant roots. And as andy said, beware of fungal growth.

If the part of the smaller plant is brown, it may or may not be a problem: squeeze it gently to see if it is soft. If soft, there could be rot or hopefully, only waterlogged and may dry up. Take them out of the soil, let sit on some newspaper or kitchen towels to dry up, in well ventilated spot (not direct sun). Make sure you get off all the mucky soil - wash it off if necessary. It won't die if out of soil for a while (even few days). How about the leaves - are they just limp or yellowish-looking and very soft? Photo would help... I am not familiar with your soil either (but many members from UK use it - hopefully they will see your post & comment), but I would mix it with min 50% of perlite. If you could get some grit, it may help, mixing approx. 20% of soil and 40/40% of perlite. Make sure there are drainage holes in the pot. Do not press soil down too hard when potting, just firm it up. Poking around perimeter of the pot while adding soil will help it to settle down. You could always use some larger rocks to support the plant after potting - while it is growing roots to anchor itself in the pot.

Kandice, your soil looks too heavy for a succulent. See how dark it is? It looks like it is retaining a lot of water/moisture. I would recommend that you pull your Aloe out of the pot - get all the soil from the roots - and mix is with at least 50% perlite or pumice. The mix will be chunkier, like this - You need a potting mix that drains well. And you must have a hole in the bottom of the pot for drainage. Succulents do not like to sit in water. Adding rocks to the bottom of the pot does nothing to help with drainage, so please don't try that. Let the plant dry out between waterings. It will do better if kept dry than it would if too wet. Wean your plant into more light. Aloes like full sun, but if you plunk it into the sun it will burn -- just like me! Your plant is longer and skinnier because it is reaching for more light. That's easy to correct. Newer growth will be tighter and leaves closer together with more light, but the old growth will not change. Hang in there! You haven't killed it in these past years so you are doing something right. Just a few improvements will help. ;-)

I posted - THIS LINK - on your other post; mybe it will help to get ID. BTW, do not be afraid of repotting plants if they need it - depending on why, they could suffer more damage if not repotted. I do not think your plant is in desperate need of repotting, rather aesthetic. Depending on species, repotting my or may not help it to grow straight - but I understand why you would want to :) Some sp, that are not trailing naturally or if trail are not that huge - like A. juvenna in your other post - will look best if beheaded to get rid of elongated stem. ETA: just adding photo, not same aloe as yours - this is most likely Aloe maculata. Some are getting etiolated - only so much space with good light !:). It is compact plant in proper light conditions. But they will be decapitated and re-rooted in Spring: