If you had a big change with methylfolate...I'd suspect you have the DNA mutation problem.

You could increase to two of them a day, and see what happens.
You already use the methylB12 so it is safe to increase the folate too.

Often when a deficiency exists and you start to repair it...there can be a "priority factor" where the body sends the newly offered item, to various spots in the body where there is need...like the brain, bone marrow, etc. So increasing a bit may give more opportunity for the folate to work.

You can add in the P5P whenever you want. I'd wait a few days to see what the extra folate does. The P5P works mostly in the methylation chemistry and formation of neurotransmitters. It is also protective of the heart. P5P is not involved with the methylation DNA transferases that I know of...but works along side with other systems.