I don't know why they go to seed. I guess stress. Having 2 1000W HPS beating down on the plants in a 5'x10' is just too much. I did ask questions on the way here and had the lights 12" above with a high velocity fan sucking the heat out. Shrugging shoulders.
I'm starting from the beginning with a 400w LED.
Under 1000W HPSs the buds were always fluffy and the weight was mostly seeds.
2x 1000w HID is not to much light in a 10 x 5. In reality, its not enough. A 1000w HID is rated to use in a 4 x 4 area. Ive been using 1000w HID since they came out in 77-78, and have always used them in a 4 x 4. Thats what theyve been rated for bny the factory, ever since they came out. I myself now use a 1000w Hortilux HPS bulb. Its 1881umole. But HID loses 10% of its output the first month of use. I use the Hortilux because its got the most umol, except for the Ushio Hi Lux which is a SE bulb rated at 2100umol. As much as a DE 1150 Gavita/Phillips. Its good for a 5 x 5 area.
A 1000w Hortilux is 62.5w Sq/ft in 16 sq/ft.
In a 10 x 5 area, thats 50 sq/ft, and to have the same power in a 4 x 4 you would need roughly 3x 1000w HID. 62.5w sq/ft would need 3125w of HID.
62.5 x 50 is 3125w.
If your plants are always going to seed, Id look at genetics, and/or environmental factors.
A Gavita 1700e is 645w, 1700umol, actually 1780umol, and Gavita rates it as a direct replacement for a 1000w HID. Thats their numbers not my opinion.
At that rate for efficient LED using the best Samsung Diodes, thats 40.3w Sq/ft to replace a 1000w HID.
A 600w HID is rated for covering a 3 x 3 area, which is roughly 66w Sq/ft
At that rate, a 400w LED with the best diodes is best to use in a 3 x 3 area.
Will it cover more?? Yes, but not efficiently. IMHO most LED manufacturers overrate the coverage areas of their lights. Gavita doesnt. They flat out tell you their light is a direct replacement for a 1000w HID, and a 1000w HID is rated for a 4 x 4 are. Always has been for 45 years.