Hey bro, I just got your PM. If your buds aren't getting fatter or denser, it's hard to tell from the pics, but it could be a couple of things. Maybe your lights are either too weak or too far from the plant. You said you were having a problem with them stretching, too, right? If your plants aren't getting enough lumens, whether it be from weak lamps, crowded plants, or lamp distance, it will cause more internodal stretching and airy buds. Also, how far into flowering are they? There's a point in flowering where the buds really start packing on weight, and maybe yours just aren't there yet. The only other thing I could guess from the pics, is what kind of nutes are you feeding? Those plants look like they have nice, dark green leaves, which means they're getting plenty of nitrogen. That's good in vegging, but not so good in flowering, depending on how far into flower; too much nitrogen encourages more veg growth instead of flowering hormones, and also causes buds to foxtail and calyxes and pistils to stretch. I'd make sure to feed either a straight bloom fertilizer with plenty of P and low N, or maybe no ferts at all for a little while and see what the plants tell you. Hope this helps.
Peace,
J Dubs