Should i harvest even tough the buds are so small ? Or wait 2-3 weeks ?

Defoliation does not cause bigger buds. Defoliation (can) cause smaller buds. During flowering, your plant needs a lot of energy to grow the flowers. Your plants only source of energy is the leaves. More leaves = more energy made = more and faster and larger growth. Hot weather has no effect on nitrogen levels. Nitrogen is a fixed element, it does not change its properties due to weather, be it hot or cold. Small buds are usually the result of low light intensity or too small pots or genetics or poor growing conditions or a combination of all four. In all honesty, a 150watt LED is not going to give you the huge blooms you are looking for. However, your flowers are still quite a way off maturity, so will still grow a bit bigger. Look to harvest when there are about 95% brown pistils, but don't stop feeding too early, once the pistils are about 90% brown go to giving just plain water for 7-10 days by which time the pistils will be 95% brown and your plants will be ready for harvesting and careful drying. No need to get hung up on results, being your first grow, think about all the things you have learned and how you will be able to apply this new knowledge to your next grows. I have been growing for 35+ years, still make mistakes (but not many!) and still learn something with each and every grow. Hope this helps, Organoman.