your Dendrobiums are hybrids and the rest period you can give them is by watering every other week instead of watering them every week in the colder months, hold on the fertilizer until you see new buds or keikis=then continue with regular water/fertilizer regimen....there are some Dendrobiums where you must withhold fertilizer and water completely from December 15th up when you see a bud or new growth and it may be watered if the roots and canes shrivel.... your plants don't need drastic winter rest
My Den-Phals get watered when dry, which in winter still is more than once a week (3" pot -the other is mounted). I use a skewer to determine when to water, as it can fluctuate a great deal depending on the season and the weather.