i wouldn't be that concerned with the voltage when it is discharged unless it is obviously too low, below what you stated. 1.99v (per cell) is not excessive.
When you check cell voltages you should charge it first, let it cool down and then check the voltage. A charged cell should read around 2.1v to 2.4v (this will vary depending on the age of the battery, the older the battery the reading will be lower obviously).

If you are reading 1.99 after charging then replace the battery.
Note: check the charger output also, make sure it is actually charging the battery, for a 24v battery during charging it can go as high as 28v or higher during charging. You want to see that high increase during charging, this verifies the charger has positive output.