is it mold or what?

And what can I do about it?

I am seeing small whiteish spots on the tops of the leaves. I can rub it off with my fingers so figured it is mold.

I am using a CAP ebb and grow system. 73 degrees average temp in the room. Two 600 watt HPS lights. 6 plants that look good, second week into the bloom cycle and they are 22 inches tall, nice and full. Nute temp is 69 degrees. 16 inch fan running 24/7. Can Fan with carbon filter runs every 15 minutes now as the odor isn't making it to the rest of the house yet. Wifes home business makes this a must. Grow room is in the basement. Humidity ranges 45 to 55 percent. I have a humidifier running as it gets to below 40 percent. ebb and flow twice a day.

I read through many pages here and see Hydrogen Peroxide as a spray to combat the mold. I have used it for a couple days but it doesn't seem to be taking care of it.

Any suggestions?
Thanks for the help.

try spraying with 1/2 milk 1/2 water mixture it shold take care of any small mold problems. If the problem continues geta sulfur burner its the best way

the baking soda spray works great,, i believe it is 1 or 2 teaspoons per gallon, i messed up and used 1tsp per quart, worked well but this would be used as a temp fix, the right way to combat this is get a bottle of serenade concentrate, its like $20 but does wonders, it main ingredient is bascillus subtillus or some shit and this is the main weapon againts PM, also what works well is a copper or sulfur based concentrate, i like to rotate products, one thing is for sure you should not spray anything on your plants after 3 weeks into flower, so hit with serenade 2 times over the next 10 days and hopefully you wont have a big problem, i say this because its almost impossible to defeat this stuff during a grow cycle, can only contain, once your cycle is done you need to clean out the whole space with one of those products and bleach the hell outa the room

Thanks for the feedback on the Serenade, I will get some tomorrow.
Also, should I rinse off the leaves after I spray with the baking soda? They now have a white powder all over them. Does that block the light, kinda like zinc oxide on the nose?
Thanks again for the responses, good help.
I spoke to a local shop here in Denver as well and they say I have been keeping humidity too high and just let it go as it will. My basement stays about 35%. What do you think?

Powdery Mildew is what it is. The powder is probably it just spreading. The problem is the pH on the leaf is wrong. I use 1 part milk and 2 parts water personally, then baking soda then hydrogen peroxide. Milk is best, baking soda is alright and peroxide sanitizes everything. Its a huge problem here in Nor Cal, guess the wine industry is where is spread. Serenade is awesome, just don't use it during flowering.

Key is prevention, lots and lots and lots of ventilation. Hurricane forces winds lol

what do u do if the plant that has the mildew is flowering u dont want funky tasteing buds what would u do??

if you still have mold at harvest,you could always extract the thc from moldy bud's (i.e. make hash)

any chance of getting rid of the powdery mildew while the plants are flowering?? anyone done it before?