Our heat lamp broke today (the second bulb we've bought) our chicks are roughly 4 weeks old. And have feathers all over except under their wings. Going to have to leave the heat lamp off tonight as it is now 5pm on a Sunday so can't get new heat bulb. Just a bit worried. It's around 15 degrees c at night (60f) but they are in the house and we have the heat on till we go to bed.