light energy converted to chemical energy is what powers all growth. nutrients merely match the light you provide and things go well.
So, if you can't add extra light, there's little you can do to increase bud size.
Fret not! it's early, so don't focus on what they look like today or in daily increments. By day 35-40 of flower (photoperiod measurement, less in autos i'd assume, since people typically count it when you see preflowers, which .. ?!?! flowering likely started 7-14 days before that point) mileage may vary per strain.. general ballpark ideas here.
try to look at pictures with at least 7 days between them. You'll see that fuzz stretch along stems a bit, then fill out more.. then start to ripen.