Photos would help in trying to identifying what pest(s) might be affecting your plants.
~ Webbing usually appears when spider mites are present.
~ White cottony blobs are usually indicative of mealybugs which can be eradicated by dipping q-tips in isopropyl alcohol (common (rubbing alcohol) and gently wiping them from the crevices and stems, leaves.
~ Scale insects can be whitish, brown, black, green ...
I'm not sure why you'd unpot and remove all the soil; I definitely wouldn't recommend allowing the root system of a plant to completely dry out ... they will die and you'd have to start over by rooting cuttings for new plants.
I don't know if Cayenne Pepper deters insects ... it works on keeping squirrels out of the bird feeders but I'm not sure if it has any affect on bugs. I keep a container of ground cinnamon in my gardening stuff for use on my orchids or other plants that get fungal infections. Cinnamon powder is a natural fungicide. I'd be real curious to hear if the cayenne pepper deters insects but I'd probably be reluctant to use it because I wouldn't want my dogs to taste it and knowing me, I'd be putting it on plants and then get an itch and rub my eye!
Hopefully others will be along shortly to offer suggestions and ideas as to what your plants may be experiencing. With all the rain, heat and humidity we've been having, a few of my plants have had issues with aphids. I've had to spray with insecticidal soap to get them under control and knock on wood, I haven't seen any the past couple of days!