Still struggling? In my case, I laid out the series and saw from the variations that I was happiest with the prints somewhere in-between.
We always hear quotes from famous teachers and references. Here's one that is not that well-known (I find no glaring fault in the publication), that directly relates to your question:
In photofacts number 24 Print Faults and how to correct them by Fountain Press 1951 there is a chapter on The Dark Print.
It lists the following causes of dark prints:
Paraphrasing the two topics that aren't self-explanatory:
-Changing paper, from one grade or brand to another requires a new test.
-Over-development won't be an issue if you always do FULL development.