it is hard to guess without seeing the results... I have followed the same process and have had great results, using Dharma fiber reactive dyes (not sure if the brand makes a difference) the only difference is that since I don't have a wash machine I do the final HOT wash with the synthrapol in the bathtub and generally hang them on the line to dry... they have been turning out great!
Typically speaking, I have seen two main causes for faded colors. 1. Not having a concentrated enough mix. Try adjusting your dye to water ratio. 2. Using old dye is deadly. I haven't a clue why, but using left over dye, already mixed that is, never fails to produce dull colors. It may seem silly to waste leftover dye but if you save it for next time the results won't be fantastic. Try mixing the dye RIGHT before you use it. Hopefully this helped!
I have been in the same predicament and thanks for your posts. I think I now know where I've been getting it wrong; I hope for better results next time.