HPS/LED combo grow-Seeking opinions

What's up my friends so I'm posting this for two reasons. To show results I got with the combination of HPS and 7-band LED lights which have worked so nicely in my opinion. Also seeking opinions on whether now is the right time To change the light period to 12/12; Plants couldn't be happier I tell ya they are the happiest healthiest plants I've personally dealt with. I have found that foliage-misting them right before lights out with .25 Tsp/Gal Of Super Thrive (basically vitamin B12) makes a noticeable difference in their posture.
Specs include: 400W HPS, and 2x 180W 7-band LEDs-- the HPS is sandwiched between the two LEDS which are each set up to slightly tilt inward to overlap with the HPS light. Tent is approximately 4'x4'x6.5' Back to the light cycle - as you can see in the pic there's room to spare on the left/right sides because the light footprints just don't go wide enough. This is 7 plants total ; 3 tall ones in the back (week 4 veg) , two babies on front left/right (on week 3 veg) , and two 3-gallon BUSHY wide plants in the middle (4 weeks veg). I'm concerned I'll need more light if I wanna run 8-10 plants. This thread was made not only for my questions but I'd appreciate any bit of input/information that more experienced growers could put on what they see.
Questions:
Does it matter that my plants vary greatly in size? (Light hogs?)
Most plants have began alternating stems meaning they've matured, so would changing to flower be a good move ? Or will I be wasting potential if I don't veg more?
Once in flower, is giving them their veg stage nutes first week or 2 of flower a good idea ? What about flower nutes ?
Is the pre-flowering phase FLUSH a must?
For the future , how many plants would the light that I specified be able to harness ?
Thank you all in advance

Edit: pics fixed

That's plenty of wattage for the space. Might be better just to put the LEDs out from the HPS to cover the sides where the HPS drops off though. Putting them together was something to try but you found out it concentrated the light in the middle too much. You wouldn't need more light overlapping the middle HPS part anyway, because it's plenty intense on its own. Maybe if it was a 250w but a 400 is pretty bright right under it.

Using veg nutes for the first few weeks of flowering is your choice, some nute companies recommend that. Veg and bloom formulations are so similar it would make little difference. There's always more of every nutrient than they need anyway. They just take as much as they want and leave the rest. Personally I use bloom for veg too. Has more nitrogen and potassium than the veg formula, just a little less phosphorus.

thank you for your post my friend, much appreciated! I've continued to tinker with the light positioning via your recommendation