When I had silkies I gave them a little light bulb when it got under freezing but with a dogloo I'd not risk the chance of fire as there is not an easy way to hang it. It helps that they have other chickens in there to huddle with.
Since you are not in a cold state I'd just go with what you have. You can give them lots of bedding in there to huddle down into and since there are 2 silkies they will huddle together. I have given hot water milk jugs to silkies before when I didn't have a good way of getting them under the light bulb. Not so hot that it burns them, but something warm to help for a few hours. By morning the jugs are very cold though.