I am at 21 days into flower with this Black Mamba and I have some rust colored spots on the tip of 1 leaf. Some of the other fan leaves are darkening. Fox farm ocean forest soil, fox farm trio, 5 gallon fabric pots. Water ph is between 6.6 and 6.8. The temps are at 69 F night time, 74 F daytime, humidity stays between 50-60%. I have not seen this before. Can anyone identify the issue and point me in the right direction for a reliable deficiency guide?