The use of digestive enzymes shuts down the body's own production of the enzymes being substituted for the body's own production. Some enzymes, including amylase, also increase blood sugar levels and calories by breaking down in this case starches in to sugar. But I really dislike cellulase and hemicellulase since they not only increase blood sugar and calories, but they also digest the primary foods for our beneficial flora starving them. I prefer to stimulate the body's own production of enzymes with things like bitters.
The average melatonin is 3mg, which is hundreds of thousands times higher than what the body normally produces on its own. Therefore, there is once again the risk of shutting down the body's own ability to produce melatonin. And the long term effects of such massive levels in the body is unknown.
5-HTP can help in some cases of depression since it is a precursor for serotonin. But not all cases of depression are a result of low serotonin, and elevating serotonin levels higher when already normal can lead to mental disturbances, loss of appetite, erectile dysfunction in men and loss of libido in both men and women. Therefore, it is best that people stick to the lowest dose possible starting out to see if they are likely to respond to elevated serotonin while reducing the risk of side effects.
And finally, don't go overboard on creatine. Creatine is high in phosphorus, which can cause pseudohyperparathyroidism if taken in excess leading to bone loss.