Unpack the theme (instructions in
this sticky)
At the top of the rtconfig.txt file, find this line:
change it to:
Save the rtconfig, refresh the theme, you will then be able to turn on the edges.
As you will see, this doesn't solve your problem. It looks like your noise threshold and/or variance are set high for the spectral peaks, I would suggest tweaking them to lower settings (View > Peak Display Settings)