Yes; there’s nothing you can dump on them that will grow big buds. Only wattage, training, and time can do that. One effective method of increasing bud mass is through light manipulation. This is probably not what you had in mind when you posted this question and it is probably too late for plants you have in flower currently but you can try this next run if you have the indoor space, patience, and adequate lighting.
Start with mature plants from seed or clones in veg phase by reducing the amount of daylight by one or two hours per week. Go from say 18/6 to 17/7 and so on. The more gradually you reduce hours of light the more it will affect bud structures. Keep going until they are around 14/10 or 13/11 when most strains begin throwing pistils. They will be both vegging and flowering simultaneously at this point. Then pull the cycle back to 18/6 for 2-3 more weeks to re-veg them. I usually transplant them into bigger pots during transition and then flip to the final bloom phase until chop. Also known as monster cropping; it works by closer simulating the suns natural cycle as it changes gradually through the summer into fall. This reduces stretch in between the nodes and increases nodal branching sites where buds form thereby increasing mass; you can easily double the yield this way if you have lighting intense enough to get down to the bottom growth.
