is my light the proper height from my babies?

I'm using 75% of 400 watts, so it's 300 watts right now. MH light.

It's about 18-19" off the base of the Aero, PPM is at 700'ish right now and I cycle the PH back down to 5.3 after it hits 6.2-6.3

Oh and yes it is cool tubed and exhausted out the room with 450 cfm

2 -5 inches from the top of the plants