Too much moisture
The most common cause of yellowing and browning stalks among Aloe plants is improper soil moisture–in particular, overwatering. Only water your Aloe when 75% of the soil in the pot is dry. In the winter, you can allow your plant to dry out a little more between waterings. Your Aloe plant is native to very dry climates and is extremely drought-tolerant.
When you water your Aloe, make sure you provide enough water so that liquid flows from the drainage hole at the bottom of the pot and into the saucer. It’s extremely important to discard any excess water in the saucer and not to let your plant sit in any standing water. Your Aloe doesn’t like “wet feet,” which will cause the roots to rot and lead to the eventual death of the plant.
Aloe will grow best when placed in bright indirect sunlight. If placed in very low light, the leaves will droop downward.
Some yellowing is natural
Is there new growth on your Aloe plant? If there is new growth appearing and the yellowing leaves are older, particularly at the bottom of the plant, this yellowing is natural. Your plant sheds its old leaves and sends energy to new growth.