If you are going to keep the body in a constance state of stress and repair, rather than allowing extra days away from training, than it's growth potential may not advance at it's best. Or even halt for some. The exception being the ones blessed with the proper genetics or using The Stuff. Recovery time, with-in a training week, is very important. The CNS (a major key to steady muscle size and strength) must recover fully to be ready for it's next workout challenge. The only thing that you might add to a successful program you seem to be on now, is more resting days off from training. That being one less training day a week, making it 4 days, rather than the present 5. That 5 or even 6 day workout scheme is going to affect the CNS in a negative way, sooner or later. You want to insure that the gains you have made will continue for a long time. That 15lb of pure muscle gain in 3 weeks is outstanding and that eating pattern seems to fit you body type very well. Just that we want those gains to progress and not slow down/stop due to over stressing the CNS. The CNS can adapt to a lot of things but it also needs it's recovery time.
I'm in agreement with HedgeHog, that training muscle groups as a unit yields faster results overall, for most people. Along with 2 or 3 times a week workouts. And have at least one day of rest between any workouts. There are exceptions of course, some select specialized programs and personal goals require more time for short periods of intense training. But only for a short period. That's why a lot of lifters will change a workout program every 6 to 8 weeks or so. Allowing the CNS to adapt to different work loads. Change can do a body good, at times.
As said here before, I'm not a big believer in added supplements. But seen impressive muscle and strength gains on some of the football players who have used Creatine (pure grade with a dextrose delivery system). Also Flaxseed, Omega-3 oil, Safflower and Olive oils show promise. Some of the players put Safflower or olive oil in a protein shake drink every day to keep their weight up during a season. Good Luck.