Yes you may need to replace some bulk. Poorer food choices that we fill up on sometimes give the illusion of adequate bm's only because one is so filled up with crap that the sheer bulk of a new meal pushes out matter from an already stuffed colon making one think that their BM's are adequate.
When we normalize the diet sometimes we miss that sheer bulk and realize that peristalsis may have been weakened by the expansion and false peristalsis that junk provided.
The bowels must be trained to move on their own so begin a bowel schedule and look into bowel toning perhaps no herbs are necessary there just retoning the muscles. Store bought Prune juice is pretty acidic and can also dislodge toxins it has that effect.
Try to utilize more healthy fats flax oil seems to work great for the dryness as well as transit time. A bit of epsom salt say 1/4 tsp before or a few hours after a meal will help. You may need to up the bulk also with concentrated foods such as grains rice, pulses etc... until the bowel is retrained. Establish a morning routine such as downing the warmed water with lemon and honey 2 cups is real good and gently sitting (heels to buttocks is best over sitting on toilet). The muscles will respond and build just as we trained our children. Peristalsis sounds like it may be weak or unable to respond properly without the stimulation of over eating crappy food and the bowels are absorbing the water from the food before the BM's are expelled.