Need some help. 2 problems.

Another 7-14 days, depending on your preferred type of effect. Now to 7 days for a more THC influenced head high, 7-14 days for a more CBD influenced body stone type of effect. Yellowing is normal at this late stage of flowering.......generally known as "the fade". Basicaly, the plant is drawing vital elements from the older leaves to use in flower growing. This is why defoliation can be a bad thing for plants,.......removal of ready made nutrients. Not switching to bloom nutrients until actual buds are growing helps prevent early/excessive yellowing. Keep using grow for the first 2 weeks after 12/12 will help this. Cannabis still needs adequate nitrogen in early flower and "pre-flowers" is not flowering, only an indication that flowering is about to commence......usually in about two weeks time.