I'd say it's the right time to defoliate, if your bigger fan leaves are more red/purple on the stem of the leaf and the leaf is larger than your palm and that leaf is covering nugs that are below, take that leaf off, more light to more buds equals bigger yield per nug. The spectrum for HPS(I'm assuming your using) is more site growth, as in the processing done at the site is for that particular site on the plant, so when you have a ton of growth on the bottom that never gets any light they never get bigger even though you have a ton of leaves on top getting light, I usually leave a few leaves up on the crown (top of the cola/branch) and work my way down defoliating as needed, your plant may look a little bare but they bounce back. Plants usually drink/eat more when you defoliate due to you taking away most of the "storehouses" or leaves. I'll have some pictures of some of mine that ive defoliated.