How often are you watering? If more than once every 2-3 weeks it is probably too much, especially with a plastic pot. From the way the plants are leaning it looks like they might be low on light too... and the less light it has the less water it needs.

I would stop watering and put the plant right in the window if possible... if you have a southern window it will probably prefer to grow there. my aloe lives on the sill of a south facing window with full sun and gets watered only when the soil is completely parched (2 weeks to a month) and only gets fertilizer once a year. It is going on six years now and is about 3 ft tall. remember aloe is a desert plant.

Rotted out from too much watering. Container also looks big, and that also retains water. My Aloes spent the growing season (May-October), and then go into a southern exposure where I water them once a month if that.

Regarding the stems you picked off. Next time save them, let them dry a few days and put them in soil in a bright spot (sun or LED growth lights) and they will create new plants. The roots they came from will sprout new growth. The plants look nice and green so it appears they are getting enough light. Just make sure you don't water them too often.

the one in the first picture is rotting. If you're not quick, the rot will spread to the rest of the plant pretty fast. Its usually from over watering. I would take the whole plant out of the soil, check the roots for rot, cut all the rot out with a sterile knife or scissors and let the wounds callus over for about a week. Then repot in fresh soil. After you do that, refrain from watering for at least a week. When you do start watering, only water when soil is completely dry. Aloes are hardy and as long as the rot is gone and its watered less it'll be fine. I had an aloe I didn't water for 2 years once and it was fine, they just go dormant. Much easier to kill one from overwatering than underwatering. Good luck!

A N facing window is insufficient light, Full sunlight would be much better, but a south facing window will suffice.

The original poster didn't reveal her location. In the northern hemisphere at 34N, I find that my exact south-facing window is too bright for aloe in the winter, when the sun is low and streaming in the south windows. It started turning reddish. So I've moved it to an east facing window, and it greened right up and grew some more.

Avoiding overwatering is important, of course. Make sure your pot has holes in the bottom, and that excess water isn't pooling in the outer pot.

I love my aloe red and in summer full sun :)