My broilers are 4 1/2 weeks old. They've been outside for the last few weeks with an attached enclosure with a heat lamp. Temps are in the lows around mid 60s. I want to start moving the chicks onto new grass but I have to take away the heat lamp. The only issues is they are definitely NOT fully feathered. Some of them look really naked with no feathers on their back or butts. Is it okay to take away the heat?