Have you done a heavy defoliation? It looks to me as if you have, as I can't really see many big leaves. Without a diary and not much info to go on, giving any advice that is meaningful is all but impossible. If you did defoliate, that could be your answer there, especially if done mid flower. Removing leaves thinking the plant will "channel" its energy into flower growth is a foolhardy concept, as the energy required to make the flowers grow, is being made by the very leaves that get removed. The buds and the small bud leaves can in no way produce/provide as much energy as is required, when/if the plant has lost all its healthy green fan/shade leaves. Less leaves = less energy = less growth. Plants can not and do not "channel" energy, all energy is used throughout the entire plant. For a plant to be able to make a conscious decision about energy distribution, the plant would need a brain or a mechanical network of energy distributing minions directing energy flow, which is obviously a ludicrous notion, so to is the theory of a plant making decisions about where energy gets set/"channelled! Unfortunately, if you did defoliate, there is nothing that can be done to restore energy production at this late stage, your plant can only produce her biggest and best flowers with her biggest and best leaves being left in place, making the energy so that she can grow her biggest and best flowers. More leaves = more energy = more growth.
If on the other hand you did not defoliate and everything is fine with your growing and feeding methods, small buds then can only really be attributed to poor genetics and if so, there is absolutely no way to alter that fact, so you will just have to chalk it up to experience. My advice would be to grow normal photo period plants next time, their genetics are much more stable and can be harvested in comparable time frames and using less electricity. I experimented with autos and had more genetic freaks with 30 pants than I have had in over 30 years of growing normal plants. These days I steer well away from autos due to too many problems and much lower yields than compared to normal photo period plants. Just veg the normal plants for 4-6 weeks, put them in flower and harvest 8-10 weeks later. Total time - 12 - 16 weeks. Autos take roughly the same amount of time but need an extra 8 weeks of 18/6 light compared to normal plants, that need 18/6 for 4-6 weeks then 12/12 for 8-10 weeks of flowering. That is 8 weeks x 6 hours = 56 days x 6 hours =336 hours of additional light over a typical grow cycle for autos compared to normal photo period plants. I know which power bill I'd prefer! Also, in future, it is a good idea to grow at least 2 plants, that way if something goes wrong with one, all your chickens aren't in the same basket.
Hope this helps,... Organoman.
P.S. Let me know if I am wrong and you didn't defoliate. Thanks.