Congratulations, it’s an exciting time! You saw correctly: these small white filaments which appear at the nodes of the branches are indeed pistils, which confirms that your plant is entering its pre-flowering phase.
Here is how I would handle the introduction of Bio-Bloom:
1. The timing for Bio-Bloom
No immediate emergency: Even if the first white hairs are there, the plant will now begin its "stretch" (accelerated growth). During this period, it still has a great need for Nitrogen (N), contained mainly in Bio-Grow.
My recommendation: You can start adding half a dose of Bio-Bloom during the next watering, but don't stop the Bio-Grow right away. The plant needs both to build its flowering structure.
2. The gradual transition
Mixture: The ideal with Biobizz is to make a gentle transition. Continue the Bio-Grow at normal dose and introduce the Bio-Bloom at approximately 1ml/L.
Observation: Watch how the plant reacts. If the green of the leaves remains very deep like on your other growing plants, the dosage is good.
3. Why wait a bit for the full dose?
Bio-Bloom is rich in Phosphorus (P) and Potassium (K), essential for making the buds swell.
Currently, your plant is still “making” stems and leaves. Too much Phosphorus too early can sometimes block the absorption of other nutrients necessary for stretch.
In summary: Yes, start adding it very lightly (1ml/L) at the next watering to prepare the ground, but keep your growth fertilizer as the main base for another good week .have nice day