What is my deficiency??

Im indoors in premixed soil, sunshine mix #4 . pH is about 6. Lots of fresh air in a 8'x8'x8' room. 600 watt HPS about 24 inches away. temp is a constant 70-71 F 50% relative Humidity.oscillating fan blowing on them too. Id say they are pretty cozy.
Feminized Bianca from AMS. Started from seed under t8 fluorescent bulbs /started on april 20. (not to be cute.)
currently in 2 gallon conatiners they are about 6-7" tall by 8inches in diameter when viewed from above.
noticed dead spots which start near the margin but not at exclusively at the tips. appears limited to older leaves and new growth looks good but seems stunted. as the affect leaves get older the tips begin to curl upwards.

PLease see pics

please help.

Your new growth looks great, that's the main thing. I see this in young plants that are kept moist, or a little too much nutes. Let the soil dry before each watering, to the point of almost drooping. You can get a feel by how heavy the pot is.

Looks like the soil has been kept to moist and the leaves laid in it.

Id say over watering / lock out