I would spray in the morning to give it time to dry the rest of the day. Maybe a bit less light also for now.

I'll start spraying it in the morning, but what would reducing light do to help? Is that a reason for the leaf burn?

I find bright indirect sun and only early morning or late afternoon direct Sun to be the best for mine.

Also try Safer brand Fungicide. I'm not a big fan of multi purpose mixes. The burned leaves will eventually die off, don't worry too much about it.

Why are your plants getting fungus? This must be solved.
Spryaing should not be a long term answer. Like taking a pain killer instead of finding out what is causing you to need a pain killer and treat the cause instead of covering up.
It isn't a good idea nor needed to spray the plant itself, in a enclosed terrarium you may be encouraging fungus growth on the plant. Constantly spraying the plant with heavy mist does it no favors.
A water spray of fine mist to enchance the look is great but spraying chemicals organic or not is zapping the vigor of the plant, without finding the cause of the problem.
This plant does fine with humidity in the air in producing dew thick leaves, which you spray it you wash them down.
D. capensis doesn't like real hot temperatures that could build up in a terrarium and likes moderately strong light.
Its not a hard plant.
There have been plants here sitting outside all winter with temps down to the low 30's and highs only in the 50's with cold nw winds hitting them and low humdity down to the 30% range which have had dew and good leaves. Though a bit ragged out looking.
Now with temperatures in the 70's and nights in the 60's they thrive with humdity still low at about 45 - 60%.
However with summer heat soon to arrive the D. capensis will go downhill due to the temperatures climbing into the low 90's and 80 at night with very high humidity and the sun to much for them.

I know humidity was a cause of the problem(they had some damp-off) and that's why I gave them more air opening the lid of the terrarium a bit. But to prevent the fungus from coming back, I only put a little spray on the crown of the plants where the fungus was occurring.

I've had problems with those "3 in 1" sprays damaging leaves on delicate plants. If you think that's the case with your plants, I'd try some alternative treatments. First, I'd be sure the plants are getting enough sun and air circulation. I'd also consider adding a little sulfur to the soil to raise the pH a bit. You might try puffing some sulfur dust on the leaves to see if that helps. This dust is sold as a treatment for fungus on roses. I've never tried this on carnivores, but I've been hearing good things about a systemic fungicide made by Bayer. That would be a last resort, of course.

My capensis plants have been outside all winter here in SoCal and they look great now. However, I also had a D. filiformis that had shrunk back to a bulb (or whatever you call that) during the cold weather. It looked like it was going to break dormancy until about two weeks ago, when I noticed nasty gray fuzz all over it. I assume that means it's been killed by fungus. Darn shame.

Oh they are in a terrarium? CPs do not belong in a terrarium. Even tropicals. Tropicals in winter should be grown in a windowsill, NOT in a terrarium.

tommyr that is your opinion and IMO fish don't belong in aquariums either but millions of people have them with success.

peace-maker-cp install a PC fan in your terrarium. Cape dews do best in or around 50% humidity. With the top closed it's probably more like 80-90% which is too high. If you have a full glass top I would remove it completely and still install a fan.Air circulation will solve your fungus or mold problems.

I now keep em' at 55-60% humidity. And I don't have a glass top, just a tank lid. The fungus is gone and the sundews are recovering pretty slowly but they're getting there. I just added a new addition to the tank...a VFT. It seems quite happy in the terrarium...nice red tint and lots of new growth.
Hopefully now I won't have such bad problems with my plants. : )

I grow my cape sundew without a terrarium, in my room at less then 15% humidity. next to my highland neps and one lowland, N. rafflesiana Giant form recovering from a cutting I made from it.

Surprised the big guy is doing fine in low humidy. I'm going to see what other neps can grow in a low humidity environment.

Really? They don't like humidity up in the 80-90% range? What about adelae?

The reason I ask is because I was considering putting one in my terrarium to deal with some little beasties. There is a fan running in there for air circulation, but I keep it at 85-95% for my orchids.

Taz6122,
Fish and plants are 2 different things. Good luck.

Ask Sarracenia Northwest (http://cobraplant.com/index.php)
if they belong in a terrarium.

I am only trying to help. Good luck to you.

I'm not going to argue and S.NW. is in a totally different zone. Their conditions, altitude, average temp., humidity, are all different and therefor care instructions need some adjustment from zone to zone. Besides they grow the majority of their plants in a GH which is a controlled environment.

It is much easier to control an environment in a terrarium than outside. And much easier to control insect population. Ask them how to mimic their conditions without a greenhouse.

Good luck!