For chemical fertilizer Hydro Gardens says when you use their base formula-4-20-39 x 15.5-0-0 Calcium Nitrate, and Epsom Salts, to feed small ever increasing amounts from seedling - up until the last 2 weeks of flowering. Also do not cut out Nitrogen during flowering. All Nitrogen is is Protein. Humans eat protein, and our bodies turn it into nitrogen. In a nutshell, Nitrogen also means of first importance.
In an 8 weeks flowering strain, and yes there are plenty of 8 weeks flowering strains. Dominion Seed Company Local Skunk being one of them, Hydro Gardens also recommends using Monopotassium Phosphate from weeks 2 1/2 or 3 until week 4, and then cut it out. Then in weeks 5-6 add extra Epsom Salts. Epsom Salts contains Sulfur, and is theorized Sulfur is responsible for Terpene production.
Then in weeks 7-8 cut the fertilizer back to 50%-60% of what you have been feeding of the base nutrients.
If you miss the window of weeks 2.5 or 3 until week 4 for adding MPK, its to late for it to help. The buds have already set.
Hydro Gardens also uses tissue analysis for their recommendations, and have been making fertilizer since 1965. They have been making Plant Specific fertilizer since the 70s.
Flushing also has no scientific basis.