Hell yeah you should run MH in last 2 weeks. No doubt. I have seen the frost. Happens fast, too. I ran 1/2 hps 1/2 mh overhead before. And it was frosty to a certain extent(would have been frostier w/something besides those 4200k broke-ass 18.00 internet lamps), but when I was taking down the room, it became too bright for the remaining specimens. So I had to dim the hps, because the hps was on digis and the mhs on magnetics that I had at that time.
And as I dimmed the hps down, and the relative ratio of mh light to hps light increased, there was an immediate increase in frost. And the more the light was weighted towards the mh spectrum, the frostier they got. Straight up.
Your lamp choice will also play a part in how much frost and what flavors predominate.
And a good mh lamp will produce a different, more complex set of flavors than with pure hps.
Anyone who would advise otherwise most likely has not played with hps vs mh in vert and overhead for months at a time.
MH will make your weed more dank. I don't know if a 10k aquarium metal halide for example with that surplus of blue would produce more dank meds than the 5k-6500k daylight metal halides. Hopefully someone can tell us about that.
I will say for a fact that my chemo x og kush was at its best under a
hortilux blue mh. Too bad those lamps are $170 apiece and have a 300 hour lifespan.
I can vouch for a positive result from the digilux 1k mh that is 55.00 at pl---light---hydro---ics.