When to switch from vegetative to flowering fertilizer?

I am growing outdoors, and have been feeding with a 9-4-8 fertilizer for the growing stage, and have a 4-8-8 I want to use for flowering. But I am not sure when should I switch to the flowering one.

Indoor you would usually switch when switching the lights to 12:12, but how do you do it outdoors? Do I start feeding with the flowering fertilizer after the summer solstice (which already happened on the southern hemisphere), since the days start to become shorter after that day. Or do I wait for the preflowers to start growing more calyxes and the plants to actually start flowering?

5 th to 7th week

My plants usually take 7 to 9 months outdoors depending on when I start the seeds. They current ones are about 14 weeks old and only one started showing more calyxes other than the pre flowers. 5th week seems a little earlier for me, the weather conditions are far from ideal for flowering at that stage, at least for my plants and based on when I plant them.

I believe most feed veg. through the stretch which is weeks after flowering starts.They still need N until then.

Aye buck, typically I get two weeks of veg growth, that’s when I trim the little stuff off in the interior.

If you are in the southern half of aus then around aus day is when they really start to turn so around then.

Wait for preflowers is what I do, but I only use liquid fertilizers for flowering and not always (depend on strain and if plants are in ground or in pot), I add bat guano at first preflowering sight and then one time more in mid flowering, but 20% or 30% of my soil is manure (cow/sheep) plus diy compost.

I have 3 periods - veg, transition and bloom. I veg for a while, til the plant is roughly half the height I want it to be. Then I transition by change the light pattern to be 12 / 12, but keep the veg bulb and veg nutes in (to keep stretch down)- do this for 2 weeks. Then l fiush for a few days. replace the bulbs with the bloom ones, and start with the bloom nutrient regime.