We would have to have more of the details of your training programs to do an appropriate post-mortem, but as was indicated by the previous post, lots can happen to undo good training. I’ve seen seasons ruined by one week of inappropriate training.
This is why Charlie was always careful to make very smooth training transitions when he acquired athletes from different coaches. He kept much of the same work in the program devised by the previous coach and slowly transitioned into his approach. He knew that the body is very sensitive to drastic changes in arrangements of stimuli.