Decreased, declined, and lessened have the same meaning in the stocks context. “Descended” is not well-suited for that context. “Descended” is better for physical things moving down from a high place. Example: The airplane descended through the clouds. The woman descended the stairs. “Declined” can also be used to describe something getting less strong or less healthy. Example: The power of Rome declined in the fourth and fifth century. Also, “decrease” and “lessen” can take an object — example, You should decrease/lessen the amount of time you spend playing video games — but “decline” does not take an object. You can’t say “You should decline the amount of time . . .” Finally, “decline” can also mean “Say ‘no’”. Example: She declined his marriage proposal.

In the context of stock value, for example : 1. The value of the stock decreased. 2. The value of the stock descended towards zero 3. The value of the stock declined 4. The value of the stock has lessened.