In my experience with mammoth p, I found for me it harms the plant if I give it in veg, but works great if I start it during flower, I think it does that from getting the plant to use up all the phosphorous in the soil, and then when the plant needs it the most, there's none available, that's just my guess and my experience, I've seen many have great luck using it throughout the whole grow, but for me it took just one time to hold back until flower, and I don't know if you've been giving mp to this one or not