From a fellow grower: I am starting to force flower my plants and a local dispensary sold me Monster Flower fertilizer. It is 0-50-35. The instructions say to mix 1/2 tsp to 5 gallons. The high phosphorus levels are a concern to me. The manufacturer says it is exactly what is designed for. Can you give me some advice? I just started to force yesterday so will go with plain water for this week.
What’s the NPK ratio of your base nutrients. Most reputable nutrients line supply enough NPK to successfully grow and flower cannabis to harvest 
Sounds like they are trying to sell you a bloom booster.
I would avoid bloom boosters and use a product that has the proper proportions of NPK and micronutrients. Bloom boosters are unnecessary and I’d go as far as to call them “snake oil.” All bloom boosters are is a stronger solution of P and K that is already in the product you already use. If you want the effect of “bloom boosters,” just feed more of your nute line’s PK product. Many bloom boosters are very salty. You will be introducing less salts into your grow medium doing this and will still achieve the effect you are looking for. Adding bloom boosters results in a mineral salt buildup that submarines root zone pH and pH becomes very difficult to manage. It also screws up your PPM readings since the NPK distribution is altered.
Well stated Grow Bro