A general dose of 5-HTP is around 150 mg, but you personally may need more or less to be therapeutic. The thing to watch for is improvement in symptoms. Some people feel good with just 50 mg, but most need closer to 150 mg, depending on what other supplements they are taking, how they are eating, exercise, sleep, etc. We are each individuals in this sense.
Brain types can change for many reasons. In addition to your exercise and supplement changes, have any environmental, social, emotional, psychological changes happened in your life in the last two years? Changes in nutrition or sleep? Work shifts? Relationship changes? All of these things can impact our brain, in a positive or challenging way.
Best! -Zoe