It very well could be your bodies response to the stress of detox.
Peoples heart rates arent static at rest. They will vary greatly depending on whether your autonomic system is heavily under parasympathetic or the sympathetic influence. This is known as heart rate variability.
For example my heart rate upon waking when fully refreshed and resting is around 52, however if I am sick or the morning following a particularly grueling workout I may see it as high as 65.