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It sounds like the moisture or humidity conditions indoors must be just high enough to create an ideal situation for the powdery mildew to grow. Neem oil can help with this. Here is more information: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm

The standard organic treatment for most pests is neem oil and may work on caterpillars too. In addition, Bacillus thuringiensis, also known as Bt, is effective for caterpillars.These articles should help: https://www.gardeningknowhow.com/plant-problems/pests/insects/prevent-caterpillars.htm, https://www.gardeningknowhow.com/plant-problems/pests/pesticides/using-bacillus-thuringiensis.htm

This article will answer you questions on columbine reseeding and dead heading: https://www.gardeningknowhow.com/ornamental/flowers/columbine/columbine-flower.htm

Some columbines do this from time to time. Problems like powdery mildew, leaf miner or spider mites can lead to leaf drop. Here is a link to an article about Columbines that you may find useful: https://www.gardeningknowhow.com/ornamental/flowers/columbine/columbine-flower.htm Some columbines seem to start dropping their foliage soon after flowering and start going dormant. Their work of producing a bloom that will then produce seeds seems to have taken all of their energy. Deadheading them just as soon as the bloom starts to fade sometimes alleviates problems like this.

Perhaps you will find some useful information in one of the references listed in this article; https://www.ag.ndsu.edu/plantsciences/undergraduate/courses/docs365/ReferenceList.pdf

I would think Zone 10 is pretty hot for columbine, although you can try them if you want. If you do try them, they should go into partial shade. Here's a list of flowering plants for your area: http://ucanr.edu/sites/mgslo/files/121954.pdf