Hello
I did some outdoor autos this year too and one of mine stayed so short it was insane! I'd say look into other diaries of the same strain and see what other's have wound up with. It does seem like many small buds versus main dominant colas.
I'd start feeding it some molasses with every or every other watering until you finish with a small flush. I did research various bud bulkers and most seem to be made up of a sugar product, kelp, magnesium, humic/fulvic/amino acids, so whatever you have around like that maybe make your own bulker. Like mine consists of molasses or agave syrup+tnb naturals enricher(magnesium)(you could use epsom salt)+ kelp extract. And it works for me.
Happy flowering