I agree the more direct sunlight the better. This is some sundews from this forums seed bank i am growing now. In a very sunny window. If your plants don't make it i suggest you get some cape seeds.
Also when you say bottled water i hope you mean distilled, a lot of the normal drinking water would kill a sundew. Rain water would be ideal too.
Then the media, I am going to guess that is peat your plants are in? I prefer a mix of peat and perlite or silica sand 50/50 to pure peat but i would not repot a none healthy plant it would just stress it more.
For my inside long term plants i prefer a mix of long fiber sphagnum moss and perlite, it seems to last longer and is less messy no standing water needed.