Individual feeds are provided by volunteers with varying equipment, spare time, skill levels and access to test equipment.
Therefore, the sound quality of the feeds isn't going to be consistent.
Since you didn't really specify which feed is having low audio levels, it's difficult to say whose issue it is.
I captured some of the Douglas county GA feed and looked at the results using audacity.
In my opinion, the audio level of that feed is perfect.
The provider has a reasonable margin between the highest audio peaks and full-scale.
Any increase in the audio level will also increase the likelihood of distortion.