I think a gradual change of hamster mix would be a good idea - the pets at home nuggets don't have very good quality ingredients (and our Robo wouldn't eat them!). I don't know the other brand. Is it the Walter Harrison one? It doesn't list how much protein is in it. Tiny Friends Harry Hamster has the correct level of protein required plus all the nutrients required and Hamsters tend to eat all of it in my experience. It's the one recommended by the National Hamster Council. It also has good sized pieces for Syrians. They do need enough protein in their first year of growth and it is quite important.
Any change of diet should be done gradually though, so it doesn't upset their stomachs, so start by adding a bit to the current mix then increase the amount added so after a week it is half and half and then changed over after a couple of weeks.
It is likely she is only eating the bits she likes and not getting enough nutrients. It's also good to give a bit of fresh veg daily. Again start gradually so as not to upset her stomach, so maybe give it every 3rd day, then after a week, every other day, then every day. There is a list of safe veg somewhere, but I tend to stick to broccoli, carrot, cucumber, cauliflower - depending what we have in although I do buy more veg now just so we have some in for the hamsters! If you keep broccoli, and carrots in the fridge they last for weeks. I keep all the veg in the Fridge - the cucumber and cauliflower only last for about a week but you can get half a cucumber.
As Cypher says that is a lot of water! I use the small mouse bottles (70ml I think) and don't even notice the level going down as the amount they drink is quite small. I just change it ever day anyway. So it could be that the bottle is leaking. Which doesn't matter too much as long as there is always water available and as long as the bedding under the bottle isn't getting damp and mouldy. A lot of bottles leak, but I used to keep two bottles in the cage sometimes just in case one emptied itself, so there was always water available.
You can also supplement with the occasional nut once or twice a week, as nuts have protein and vitamins and it's a nice fresh extra treat. Harry Hamster already contains Monkey nuts - I give half a brazil nut once a week and the occasional half a walnut or pecan nut.
I tend to put the veg in a different place to the hamster mix - in a sputnik or on a separate little dish in a different part of the cage - it makes life interesting and they tend to go straight to the veg each time and know where it is.
https://www.viovet.co.uk/Supreme_Har...sty_Mix/c1104/