Muscle holds more water than fat, therefore when your using the gym every day and working out the muscels then your holding more water in your body through that, you will probably find that 1lb gain is just water retention and will work itself out of your body by tomorrow, also did you have 'heavier' food yesterday? you may of stuck to points, but if you have a bigger meal the day before WI then you will find that the weight of the food sticks in your body for longer, that's why i don't like having a big meal or sticking to points fully the day before WI as i find it triggers off a gain for me tbh i wouldn't worry and you should be pissed off, i know its disheartening but within yourself deep down you know it's not a proper gain and will be gone in no time at all probably along with another lb or 2, read the topic on how exercising has proven to not help to lose weight also, it does help to tone up, but doesn't always mean weight loss .. well thats what they say anyway!