I don't believe in such things, come man maybe it was just a coincidence that the marks had happened always on Monday. For me the best day to buy bitcoin is when you see it on sale and you have the money to buy at your fullest
Most people get their paychecks on Fridays, that means more to spend and pumps the price a little. This small demand boost drying up by Monday seems completely possible, just seems like something that's not completely illogical.