Tying them over will allow you to use the light more effectively, and increase yield. Will allow to bring the lights down closer to the top of the canopy.
As far as feed, not sure how they feed, but if feeding chemicals Id give a slow, weekly, ever increasing PPM of everything. Base formula NPK x Calcium-Micros x Magnesium Sulfate/Epsom Salts.
Base formula, ect, Epsom Salts will increase each week until week 6 of flowering.
Week 2.5-4 in an 8 weeks flowering strain I give a 0-52-34 boost, along with base formula, Epsom salts ect
Weeks 5-6 Base formula is still slightly increased per week, and an Epsom Salts Boost is done.
In weeks 7-8 food is cut back 40%-60%. But never eliminated. Epsom Salts/Magnesium Sulfate helps build terpenes. Sulfur is very important.
Tissue analysis says weed likes a 1-1-2 NPK ratio.