Hi, I potted some Dahlia tubers the first week in March and left them on a sunny windowsill. They were coming on great and I cut them down a couple of weeks ago and put them outside in my walk in greenhouse. Some of them look like they are willing and the leaves are turning brown and some of the main stalks look hollow. I'm not sure what I'm doing wrong but I would love to be able to save them! I'm not sure if its the weather as it has been cold at night, I've been leaving them out in the sun through the day then last couple of days but nothing seems to be helping. I fed them with tomato feed yesterday. Any help would be appreciated! Thank you!