Hi Lucinda, BETTACHKALOVE had asked me to come take a look.. I don't have a whole lot of time right now to go into too much detail as I'm about to head out, but will see if I can understand some more of what is going on.
At first it sounded like she was just going to the bathroom.. since you said it was brownish strings coming from her anus.. that is her going to the bathroom and normal. The fact that you are seeing it means that she is not constipated.
The white could of been her having absorbed some eggs, which will turn their waste white in color. Very common in females, very normal.
Is there any chance at getting a clearer picture of what you are talking about with her stomach? I am having a hard time picturing it in my head... and the first two pictures look normal other then a big belly. I see no fuzz..
You should be feeding daily, how much of the food are you feeding when you feed?
Personally, to me it sounds as if over feeding per meal.. flakes you have to be careful with not to over feed, it's hard to judge correctly the amount.
Unless it says different, that tank looks more like a gallon- I think they come in half and full gallons.
1 50% and 1 100% water change per week is recommended for that size..
Again, I am sorry I can't spend more time.. but will check back in later. If you can get a clearer picture, that would be helpful as right now it could be a couple different things..