MH or metal halide is not the normal option for flowering & as Bonsia mentioned MH in general is for vegging... this may explain why some substandard bud growth has been brought to attention in past posts to which i believe we are more on track on solving the problem.
MH or metal halide is common for veg growth from seedling to late vegging as the colour spectrum of these bulbs support the blue wave lengths which is quite suitable for this particular growth phase, now this might be translated to kelvin it is just another measurement of light i think MH is around 5000k but has higher peak in the blues you can get cfl or T5/8 tubes with greater rating around 6500k this is good high end blue spectrum & can away get with far less wattage than MH over all, but these bulbs need to be hung a lot closer due to the inverse square law of light effect.
Yarp just some minor waffle but in essence essential to the good grower
HPS is used for flowering with most of these types of bulbs being around 2100k this is more red spectrum of light blending with orange/yellow... lots of charts out there to take a gander at, but ye this promotes better flowering in the long run.
That is basic light spectrum stuff for growing bud.
Now 750w of MH for 10x12 aprox don't really sounds like it is cutting the ice a great deal but how ever you have some thing good going with conditions & the plants grown.
In real practise some may use 4 to 6 x 600w hps for that space with 2 dozen plants etc so ye you have lots to work with plus more bulbs/wattage the greater the heat meaning better ventilation.
On a side note - some minor details about bulb size/wattage to hanging distance & aprox light foot print/area of coverage to do some home work on.