decreasing light wattage at the end of flowering

Hi all,
I have 7 plants that should be ready to harvest next week. Most of the pistels have turned brown and we are at about 25 % amber trichomes. My 600w hps bulb burned out this morning during the light cycle of 12/12. I ordered another today but in the meantime I hung a 250 MH light over the girls.. Will this lower wattage hurt anything at this stage?

I would think it will just slow the plants growth rate. Less light to do their job.