Milk, I haven't heard of. Baking soda though, I have, dissolved in water. This changes the pH of the leaf surface and makes the conditions impossible for mold to grow. But I don't know a THING about that method, try googling 'baking soda plant pest'. And use the heater first.

Extra darkness is far better than extra light.

The coldest time of night is from about midnight to just before dawn. I run my lights about 9pm to 9am; they come on an hour early for daylight savings time (I don't make the switch) so in the mid-winter they are on from 8pm to 8am.

And PC, can you PLEASE stop being so argumentative?