USE THE SPECTRUM ANALYZER CORRECTLY
It is particularly important when mastering to work with measuring instruments. Spectrum analyzers provide information about the frequency distribution in the mix, goniometers show the phase position and loudness meters reliably inform whether the “loudness” of the material matches the genre and the intended target medium. In the mixing process, however, I would advise against using analyzers too excessively. If an audio signal has disturbing resonances, these can only rarely be detected on the analyzer, as they are often hidden by desired overtones. Our ears are much more sensitive than any measuring instrument! Many equalizer plug-ins have integrated spectrum analyzers. If possible, you should deactivate these, because they easily distract from the important thing - your hearing.
If you want to assess your entire mix in comparison to a reference or verify whether certain frequency ranges are under- or over-emphasized, the analyzer can be of good use. Try to subtly emphasize or lower the corresponding frequencies overall and check with your ears whether you like the result. The same applies here: hearing is the final authority; a linear frequency response is no guarantee for a good sound. On the contrary: Reggae or Hip-Hop productions, for example, often have a massive bass boost. In these cases, this is a stylistic device and not a shortcoming.
Under no circumstances can an analyzer replace an adequate listening situation. Choose your monitors carefully and put effort into the acoustic design of your workplace. Headphones can also be a valuable help if you are not entirely sure about the performance of your speakers.