AN SensI Grow / Bloom A+B interchangeable?

Good question — lots of people run into this when they get uneven use of Advanced Nutrients Sensi Grow A/B and Sensi Bloom A/B. Here’s the breakdown: Sensi Grow A and Sensi Bloom A are indeed almost identical (both ~3-0-0, calcium nitrate + micros). That’s the "Part A" consistency you noticed. The difference is in Part B: Grow B (1-2-6) is skewed toward nitrogen and potassium, with less phosphorus. Bloom B (2-4-8) is heavier on phosphorus and potassium, tuned for flowering demand. So if you try to "make Bloom B" out of "Grow B" by doubling, you’ll still be short on phosphorus (P), which is critical for flowering. You’d also risk throwing the N:P:K ratios off, leading to excessive nitrogen late in flower (stretchy, leafy buds). What that means in practice: Using Grow A in place of Bloom A → fine (they’re essentially the same). Using Grow B in place of Bloom B → not ideal, especially deep into bloom. You’ll starve the plants of phosphorus and overload nitrogen. Doubling Grow B to “fake” Bloom B → won’t fix the missing phosphorus, and could make things worse. Safer options: If you must stretch what you have: Use your Grow A + Grow B for the transition/early bloom weeks (1–2). Once buds set, you’ll want that higher phosphorus, so supplement with a PK booster (e.g., Advanced Nutrients Bud Ignitor, Big Bud, or even a generic PK 13/14). Ideally: grab another bottle of Bloom B. It’s the part that really matters for flower formulation. Keep feeding at half-strength like you are — less risk of imbalance showing quickly. Bottom line: A parts are interchangeable, but B parts are not. If you substitute Grow B for Bloom B, compensate with some extra phosphorus and watch nitrogen levels. I hope that helped 😘