I used to mist my plants to raise their humidity since i live in a 15% zone. It worked well during the vegetative period, but it was essential to use nonchlorinated water(leave it sit out for 24 hours) otherwise it burned my plants.
Being you're low humidity it could be helpful, can you place a clear cup over these babies to have a makeshift humidity dome?
If you mean a nutrient spray, definitely dilute down to 1/4 dose maybe lower and always spray at the end of the day before darkness. The 10 week bud plant would maybe do better without, otherwise keep up airflow so no rot sets in.