Your buds are small because they have a while to grow yet. When did you start flowering? You have a lot more than 2-3 weeks left by the looks of it.
Bat guano is an excellent flowering fert. Molasses is good to. Molasses feeds the soil organisims, which in turn feed the plant.
Read about molasses>
http://www.onlinepot.org/grow/3lbsMolassesManual.htm
Here is how you do it. - by Ohsogreen
First use only unsulphured molasses, like Briar Rabbit or Grandma's Molasses (brands). Mix one ounce to one gallon of chlorine free water. If you only have tap water, let it set for two days & 99% of the chlorine will evaporate. Then you can add the molasses.
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You can bubble (oxygenate) it using a cheap aquarium pump & air stone for at least one day. Or just pour it from one clean container (jug or bucket) to another a couple of times a day, for at least two days.
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This provides extra oxygen to the good micro-beaties, they then eat, mutiply, & kill off - the not so nice micro-beaties. The longer you oygenate this mix, the more good guys you end up with. Their eating & pooping out the NPK (bioconversion) is what make it highly soluble. Over time their bioconversion reduces the N and pumps up the P & K slightly. Not a big shift, just a point or two.
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This makes a good growth stage fertilizer (that's cheap).
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Just mix it light the first time & water in lightly - like one quart per plant.
Start low & build slow. This prevents overfertilizing.
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Use this mix one week & plain water the next.
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You can add nutes to the mix, but remember your adding to a mix with a NPK of about 5-1-3 already