They do look healthy, but I have been growing with guano for a while now, and it looks to me like you are not giving them enough nutrients. When I get into flowering I am usually using over twice the recommended amount as on the package, and I have never burned my plants using guano. I use sunleaves seabird guano through the whole grow, the all purpose(high nitrogen) with the seabird in veg. In flowering I keep using the seabird, but add the Jamaican(high Phosphorus) instead of the all purpose guano. I make a mixture of about 2 parts worm castings, and one part of each of the guano I am using. For plants in 5 gallon pots, I give them a half cup of this mixture about every 2 weeks until about week 5-6 of flowering. I also use compost teas during veg and flowering. Tea is: 5 gal r/o water 1 cup worm castings, 5 TBS molasses, 2-3 oz of liquid humic, 2-3 oz of liquid kelp extract. Sometimes I add a little guano to the tea, once during veg, once a day or two before light switch, and once during the first few weeks of flower, 1/2 cup of each guano per 5 gallon. The photos above are of my current Lavender Diesel grow. The plants are in the middle of week 5 in the pics above, and were grown in the method described above. They are already nice and fat, and I expect will pack on a good deal more heft before harvest. Give your plants a nice good dose of some high phosphorus guano and a nice batch of tea with kelp and humic and I bet they will start to pack on some weight. I can tell by the size of your fan leaves that you have been not been giving them enough nutrients through veg and also now in flowering. You can still burn a plant with guano, but it is much harder to do, and those girls could use a bit more juice.