Its also a good idea to combine both Calcitic Lime, and Dolomitic Lime at a ratio of 2/3 parts Calcitic Lime, and 1/3 parts Dolomitic Lime. That way you supply both Calcium, and Magnesium at a good clip, and ratio.
Calcitic is also preferred for faster PH changes.
Promix BX-HP uses both types of lime, and in those ratios. I use the BX.
It would also be a good idea to add Kelp, and Azomite to your mix. Kelp will supply extra Potassium, and trace minerals, and Azomite will also add extra trace minerals.
Also dont cut out Nitrogen when you go to flower. If your using both the Natures Own Guano veg formula, and flowering formula. Add the flowering formula to the veg formula. Dont cut out the veg formula, and use the flowering formula as a single source.
I myself would just use the 10-10-2 and added Kelp to make up for lack of Potassium, for the whole duration, and skip the 1-9-1 alleged flowering formula. All they need is a basic ratio of nutrient rich soil from start to finish, with possibly some benefit of adding a small amount of both Phosphorus, and Potassium in weeks 3-5 in an 8 weeks flowering strain. Also make sure they get Magnesium on a regular basis. Weed is very magnesium hungry, and Magnesium is the #1 known deficiency in container grown plants. Id use Epsom Salts. It also supplies Sulfur, which is known to be beneficial to Terpene production.
The above Lime combination will also go a long way for insuring an adequate supply of both Calcium, and Magnesium.
Get some Promix BX, or HP if you can. The HP is more porous, the BX holds more water. I prefer the BX under 1000w HID