CryptoConfusion; Another part to my CryptoTab experiment

As most that have read my posts know I've been looking into CryptoCurrency and how it can benefit my future and then I started to see something that wasn't really making sense to me. The cryptotab mining numbers started to change on their own as if they were being played with behind my back. So I started documenting this little change that I noticed. At first it was a change of 3-7 cents but then it became larger portions between 12-22 cents. Now I'm not the smartest person in the world but I'd like to think that I am smart. So if I've mined consistently for about 6-7 weeks and I'm only gaining cents on the dollars that I've invested then it's not the greatest but it will turn into something over the months to follow. So here I am seeing that the approx. amount that I've mined is at 3.033 for about 3-4 days and so i'mhappy to se something out of this. I don't wirthdraw i leave it there and come back 2 days later and it's dropped from 3.033 to 2.885 .... How is this possible? Are there fees that I'm not seeing? I'm so baffeled and I've been looking into this on my own but now I've seen for the 3x that it's dropping still. Anyone out there with knowledge about this please drop me a line.