Egg Mystery

Ok so we have 4 chickens. They started laying the week of Nov 16th while I was out of town. So far we have consistently gotten 2-3 a day - 1 green and 2 brown. We hadn't ever gotten more than 3 a day so we were guessing someone isn't laying. We were getting 3 more often than 2 for a while (I made a chart to try and see how many chickens were laying) and the size of the green was consistent and we were consistently getting 2 different sizes of brown ones. Then it went down to 2 more often that 3 (it's getting colder). Yesterday Moga & Matey found 2 eggs (1 green and 1 brown ) when they checked around noon - Matey loves to check for eggs. Last night I didn't see any eggs and this morning all the straw was even and I didn't see any eggs then Moga and Matey went out around noon again and there were 4 brown eggs. You might be asking yourself so what is the mystery? Well you see chickens generally lay only one color of egg. So even if the 4th chicken fianally started laying (which would be great) we still have 1 too many brown. And when Tami went out their were 2 nests 1 with 1 egg and 1 with 3. Neither nest was there when I went out this morning. A nest is just them moving some straw out of the way so it wouldn't be hard and they can move eggs around but I am wondering if maybe they laid 2 yesterday and covered them then made a nest in the same spot or what is going on. Anyway you look at it, it is weird. Anybody wanna pay for a camera for me to put in the hen house???