Do water quickly after you add the vinegar, also. Over time, the pH will rise as Al has indicated, so you're watering with 7 or 7.4 or even all the way back to 7.8 before you know it. If you test 24 hours later, you'll be surprised at how much it has risen. I used to test it, now I just go by a few plants that are sensitive. When they start to lose their deep green color on the edges or veins, when my red backs disappear, etc., I know I need more vinegar. The water out of my tap varies from 7 to 8 over time; I'd have to test it every time to keep up. Looking at the plants seems easier. I now just use 1/2 t per liter (so 2 t per gallon, approx) and water immediately. I haven't had any issues with leaf color in many months doing this.

Dogma is holding firm to the belief that something could neither be a conceptually or practically superior practice because you believe something else seems to be satisfactory - 'works for me'. Old beliefs are like a pair of old shoes - we often value their comfort so much we tend to ignore the fact they're full of holes. Almost everyone prefers the relative comfort of belief to the exercise of reason because believing is easier than reasoning; which brings us full circle to why there are so many more believers than thinkers. My $.02 I'm pretty sure you're not suggesting that a haphazard approach (a little of this and a little of that, even though I know neither what the plant needs nor what I'm giving it) is a superior approach to a well-reasoned supplementation plan. Discounting all reason because we're satisfied with the status quo is self-limiting by default. BTW - if Punky's trees are in pots (don't think that was made clear), moving closer to how nature does things is an exercise fraught with obstacles. Growing in the ground and growing in pots are widely divergent cultures. On a scale of 1-10 with growing in the ground being a 1 and hydroponic growing a 10, conventional container culture is probably a 7 or 8. Al

Thanks everybody for the input! I didn't mention it was an experiment in my OP because frankly i don't really consider it one. this is my first (now of 3) carnivorous plants and i am using what i already have to grow it. if it won't grow, and if i kill it, that's fine--then i'll know my tap water is too hard for these plants. until then, i am still going to keep doing what i'm doing.

I'd watch the watering schedule, if it were me, the surface of your soil can be dry, but it can be really sopping underneath. Something that your trees won't have is a lot of evaporation due to the airflow, so you don't need to water as much indoors. You want to check moisture level about 6 inches down or more depending on the depth of your pot. If it's still moist that low down then don't water until it's on the drier side. Trees need water when they need it, sometimes you may find it's only 5 days before you need to water, sometimes 14-16, it really depends on ambient conditions and the tree. I note that you say that you empty the trays. Trees DO like some humidity so something that can be helpful is to fill your trays with large rocks or put your tree on pot feet in their tray to elevate the bottom of the pot off the tray. Then water as usual. The water will evaporate and provide a little extra humidity to the tree, and the elevation will prevent the tree from reabsorbing that water. Also saves you a bit of work. Just a few things I've observed.