Problems with 12/12
If you switch to 12/12 before pre-flowers have shown then you may encounter the following problems.
✓ Stress related sex problems (Hermaphrodites)
✓ Abnormal bud growth
Stress related sex problems MIGHT produce hermaphrodite plants. The stress of what is sometimes called "early flowering" (it is not really early flowering, there is no such thing as early flowering. We will explain this in a moment) triggers the plant into a situation where it thinks that its chances of reproduction are slim to none. That situation is a condition called - 'self-pollination'. It does this by producing both male and female flowers on the same plant. The male flowers then pollinate the female flowers which will eventually produce seeds. The reason for this is that the plant notices that the photoperiod is irregular and that it should no longer be in the vegetative cycle but in flowering. This shocks the plant into a last ditch effort to receive pollen because it feels that it has missed its chance to receive pollen already (in the wild males release their pollen just around the time that females begin to flower and sometimes even before that).
Hermies cause problems because they may carry the hermie trait with their offspring. In fact, genetically the hermie will only produce female seeds and hermaphrodite seeds. It will never produce a male seed. If you have ever seen all female seeds been advertised by seed-banks then you should have the right to know that these seeds come from female plants which are stressed into producing male flowers. The plants then self-pollinate themselves and the results are female and hermaphrodite seeds. In a special case a female known as an XX female will produce more female seeds than hermaphrodite seeds. That is how female seeds are created. In general growers try to keep away from any hermie plants because they will spoil a Sinsemilla crop. Also having pollen floating around in your grow room from a hermie plant will spoil everything else including breeding projects.
Abnormal bud growth is a side effect of this. Because the plant produces male pollen sacks in with female flowers you may notice that the bud looks different. Also the quantity of female bud produced is decreased because of pollination.
Get the best out of your plant and wait until your plant starts pre-flowering before switching to 12/12.