There's no such thing as too much agitation _providing development time is appropriate_.(posted 8540 days ago)To translate, if you have a satisfactory development time based on agitation of five seconds every 30 seconds or 10 seconds every minute, if you then change to continuous agitation you'll need to reduce the time by around ten percent. Otherwise you'll have negs that are overdeveloped and show excessive contrast and graininess.
And you need to take a look at development time. Generally, the negs should print on grade 2 to grade 3 paper or if you're using a dichro enlarger, 25M to 40M filtration. When using small format it's often good practice to develop it a little less with the target of printing most negs on grade 3 paper; this decreased development reduces graininess and makes tonal rendition a little better.
So consider what grade paper you're printing on or dichro settings. If you're printing most negs on grade 2 to grade 1, back off development around ten percent or reduce the agitation to two or three inversions every 30 seconds.
You mentioned Perceptol. Usually a fine-grain developer such as Perceptol or Microdol-X used straight requires a lower film-speed setting to be used, or iow, the effective speed drops and the film needs more exposure than its ISO rating would indicate. If you're not doing that you could be underexposing the film; if you then overdevelop or print on higher-contrast paper to compensate that'll also increase graininess.
The C-41 and E-6 processes are designed for continuous agitation and development-time recommendations are based on that, while b&w development is usually assumed to be with intermittent (5 sec/30 sec) agitation and development recommendations are based on it.