From what I understand Green Cleaner can be used up to the day of harvest. I haven't used it that late but when I have it has work great. Kinda pricy tho
I changed over to fabric pots bc of temps. The airflow does help. They were pretty cheap for 5 gallon
http://www.greenerhydroponics.com/1-2-3-5-7-Gallon-Fabric-Pots-_c_599.html