The plant you show has several weeks left before it's ready to harvest. Go to a nursery and get a blooming food. A good blooming food will have an analysis of around 0-57-10. Notice the first number is 0, that's nitrogen. It should be 0 or very low. The second number, Phospate, should be high. The third number is Potash. You may not find a food with this exact ratio, just get it as close as you can, as you really don't have time to buy something the regulars on this site would recommend. The buds will firm up, the plant just needs more time.
Peace

Tex