Few questions after a "bad" outcome on yield

[kneegrow]

Well i finally got a bac outcome on yield just 2 ounces off each plant when the same strain i recieved 4 and half on the last one... i would just like a few questions answered as i now realise how stubborn i have been

what's the perfect PH level for a plant... and does the PH level vary from strain to strain?

Has anyone grew: Emerald Triangle G13 x Blueberry Headband Feminised Seed before as if says they grow tall, Does this mean in the vegetative stage or flowering stage? as i understand some grow more in flowering stage...

how many plants should be acceptable room for: 0.6 x 0.6 x 0.8

Thanks in advance

 

[rillos]

There are a lot of reasons but more info on your grow will help.

 

[Antics]

5.8 Hydro/soilless. 6.5 Soil

Could mean one or both. Some plants will grow 2-3x their height in flower.

If that's meters .6x.6x.8 I'd personally only grow one plant.