Is this heat damage? (Pics inside)

Yesterday I saw two tiny yellow spots on just this one plant. It looked like heat damage so i raised the light up 2 inches. (This plant is growing super fast, on average 1-1.5 inches a day.) Now today the spots are a little bigger. Should I raise the the light more?

I just want to make sure this isn't a different condition.

Thanks for helpful replies!

What wattage are you using?

"Under most circumstances a 1000-watt lamp with no shield should be kept no less than two feet from the top of the canopy. A 400-watt lamp can be placed as close as 15 inches. A fluorescent tube can be placed about six inches from the top of the plant.

The distance is not to protect the plants from the lamp's brightness, but from the heat that it generates. At its peak, the Sun is brighter than even 1000-watt lights. The amount of light measured 24 inches directly under a 1000-watt horizontal HPS lamp with high efficiency reflector measured about half of what a plant would receive at noon on a cloudless day in early July at the 38th parallel. It would equal the light intensity of a September day at noon, when the flowers are ripening. "
http://www.cannabisculture.com/v2/articles/2585.html