How to increasing bud size on Kona Gold and White Widow

I am on my 4th harvest. I recently increased my flower chamber from 2x3x6 feet to 4x5x7 feet. I continued using a 600W HPS light in flower chamber. I have 400W MH for veg, cool flourescent in clone chamber. Other than the crown or main bud, I am mostly getting airy smaller buds.

This is my first grow in winter and in the new room and find the temperature is running about 10 degrees cooler than I want (about 62 degrees).

What should I change if I want to increase the bud sizes of my plants? Should I add another 600W HPS, add a heater to warm the room up more, or lollipop the plants, or something else?

I am using general hydroponics nutrients in an ebb & flow hydro setup.

Any feedback is appreciated. I can say that the medicine I get is tasty and provides a great high. So maybe I should except the size of the yield as is.