I went from veg to flower nutes when the buds stopped fattening a base and began upward. Still 2 feeds and one water a week. Soil went from about 6.7 to 7. Heavy P and Ph in the soil, light N. 100w light moved to 28" above plant top. Went from 16/8 on the light 3 days ago to 12/12.
My impression (wrong) was that autos go one way fast and if you miss something weII that's that. I had some light calcium spotting and first days of flower some reddening on the leaf edge but since then nothing new as far as symptoms. I added lactic bacteria from the hydroponic store in the drip trays under the pots because it smelled like rotten death asshole if you moved it at all (3 hours... GONE).
The next seedling has way less drainage and tests N heavy, Ph light, P light. Handfull of bone meal in the top of the soil down to 3". Just got second set of non-seed leaves.
Personally I never push veg nutrients on a flowering plant. About a week after development, I switch.
I also feed consistently. I only water the last 2 weeks.
I have high ph well 8.5ph, so even with good nutrients

some times a bit of ph down to put me on range of 6.3-6.5.
My soil will still fluctuates a bit high also. 7-7.5 range even with flushes.
So I stopped fighting the soil ph as much. I have noted that ph up and down is only stable so long.
I would also lower the light. Big time. 100w is not enough. It it will get you something. I would have it within like 4-6inches of that small plant. I would also Only go-to 12/12 for a photoperiod. NEVER an auto. Autos I always push 18/6 or 20/4 depending if it like the light. You only get one shot with an auto. That's why I lean photo, but always have an auto floating around.