First, If your plant is in decline, whether Triffid Park says the tap water in the area is OK or not, I would definately not use it, I would switch to Distilled.
You see, what you combat when you boil water is Chlorine and Chlorimine, (Chloromine being a longer lasting more complex form of chlorine) If your water supplier used Chloromine, there is no way to remove it short of a chloromine removal agent you can get at your local fish store.
Chlorine however can be removed by bringing water to a hard boil, airating it for a day or two with an air stone, or simply letting it sit out, uncovered for a week.
The problem is, Chlorine and Chloromine are NOT your enemies, yes, they can and will damage your plants given an opportunity, but the real culprits are salts and minerals.
Now, I am guessing if you have been doing this since june, your salt content is low, as nothing kills faster... As far as Minerals go, they are probably in EVERYONE's tap water, and 'death by minerals' speed of death depends on where you live, in Texas, where our water is pumped right out of a limestone aquifer, and you can see the lime swirling around on the bottom of a glass if you let it sit for a day or two, death is almost immediate, within a couple of days, where you are though, it may take a long long time...
I think the problem with your flowers dieing really was a lack of enough energy from the sun, not a big deal, your plant can live without them... but I would highly advise you to switch to distilled water, the first time, run an entire gallon through the flytraps pot to fllush out it's system, form then on, you can use it more sparingly, keeping the tray topped off.
Distilled water is not a really big financial investment when your talking about one flytrap. If it really is to much, then buy a gallon now, and flush the media, then water as you have been, making sure your water reaches a hard boil EVERY SINGLE TIME, and then flush it at least every other month...
Using that method you will need to repot every year after it comes out of dormancy.