Lighting Virgin cultivator unsure when to switch the the bloom switch on

[Mr greenhorn]

Hi Afn clan I feel stupid for asking but I've been struggling to find information on when the best time to switch my bloom lighting on.
I have a green crack auto and a sour diesel auto both at 4 weeks old, in pre flower at the moment. I can see a few pistols on pretty much each pre-flower, should I wait till I see some proper bud formation or is the best time to hit her with that red spectrum now?

Also they're both quite short..about 10".
I have done some low stress training with both but I thought they would have stretched more by now.
Obviously being my first time I have no reference to compare to, and looking around other grows there's a lot of variables involved, strain/growing system/nutrients/experience so I'm unsure if im doing ok or they're a bit behind what they should be.

Any help is greatly appreciated

Thanks

 

[AutoWonders]

Something to consider, before I changed to cobs, I ran my mass built led lights 24/7 at full spectrum start to finish.

 

[KonopCh]

Yea, just turn them full on when plants are little bigger. So around 3-4 weeks.

 

[KonopCh]

Yea, just turn them full on when plants are little bigger. So around 3-4 weeks.

 

[Mr greenhorn]

Ok cheers for the info guys