I see 12-55-6 on the bottle, and your girls have bud set and nice healthy foliage so they are ready for a fert such as that. It would be better if it had less N but it will do, your buds want phosphorus, and lots of it! Unless you have a TDS meter I wouldn't use 2 tsp/gal to start. I would actually do 1/4 that, so 1/2 tsp/gal, then make sure you pH adjust that, because anytime you add a high P bloom fert, the pH will drop (P is acidic). Start with that 1/4 strength solution and if the plants don't burn, slowly increase it until you see signs of nute burn. I would only use that solution every other watering BTW, and only and only then add it after you have moistened the soil with plain water.