DrG is correct, variance is what you are seeing. When you tally your daily returns also look at the number of blocks solved in that same period and track that. Then you will we the impact of longer block times from difficulty / luck issues.
IYFTech is also correct - strange how you don't comment on that eh?......

Why would they again comment on the same old troll post for that is what it is. IFYTech doesn't want an answer he just wants to post the same comments over and over.