Put on flowering?

It's time to flip now imo. Switch over to your bloom nutrients and let her do her thing. I like to see a strong preflower before I switch.

It all depends on the size you are after, you can launch them into flower whenever you want, even from seed although if you do that it'll be a teeny tiny plant.

Switch to flower when your plant has reached 50-60% of the allowable room you have to grow in, some strains will double in size when in flower. I plant can be triggered to flower essentially at any point beyond the seedling phase, when is up to you and the available room for the plant to finish in.

It also took a long time for me, 6-7 weeks. But now they are flowering. Yours look like they would need another week. The fact that the plants are going into bloom very late can be due to temperature, humidity, CO2, or poor lighting.