I’d listen to the other two, but for my first grow I noticed a very big difference in bud density for a same strain plant taken just 2 weeks later. The pistils swell and retract - causing my buds to be much more compact for just 2 more weeks of patience. The thc sacs looked almost the same 2 weeks apart - but the buds swelled. Good luck!
A friend who got me started swears they will shoot pistils 3 distinct times at least. He always has fat, rock hard nugs. So even if they “look” ready, as long as they are still healthy, they may still add weight.
Are you introducing too much fertilizer? Remember, when they give a recommendation on the bag/bottle/jar, don’t start off with that amount. Depending on the nute line I use I will only use 1/4 to 1/2 the recommendation until they become older. Adding too much will also produce airy buds due to the plant locking out certain uptake of nutes.
Half of your problem is that you’re using Mars hydro which has to much blue for flower , its to similiar to spring light where you want red light more similiar to fall. The other half is medium and or watering, underwatering can produce slightly larfier buds , and a good coco coir makes you very resistant to overwatering letting you be far more aggressive with watering and nute delivery.