Lighting question

hello.
am actually using a 400HPS on 18/6 in my grow room using EBB hydro.
wanted to know if the following would help my plants grow faster, more volume after taking clones.

should i use another 400HPS on 18/6 added with the another one??
meaning would my plants grow faster with 2*400HPS for 18/6 ??

or

should i use one HPS for first 12/12, and the other for the next 12/12??
meaning my plants would get 24Hours 400HPS non-stop??

finally = would plants grow faster with more light or with having light more time??

REGARDS

Well you need to stop doing 18/24... needs to be 18/6. Any time you give them more than 11 hours of darkness they start giving them flower hormones. You've got your plants switching back and forth stressing them out.

They will grow faster if you use both lights at the same time

THANKS. so greater amount of light is better than longer light period

Use the 18/6 schedule untill you want flowering, then switch to 12/12. But i recommend using both lights at the same time.