Tang #1

So a plant stretches for a coupe of different reasons the main one being its looking for more light these lady's are filling out nicely because they aren't searching for the light so they can focus their energy on growth and flower production . Some strains stretch a lot more then others so with that in mind its always a good thing to get a rough idea of how tall your strain can grow indoors and out doors . I would wait until they start flowering full force you will see some stretch then . I hope the information provided helps a little bit -Happy Growing !

A plant will grow right into a strong light during stretching if you're not careful so not it won't prevent stretching because plants are ridiculous like that.

Hello ! With your 615Cmh then the best distance between the top of the plants and the lamp should be around 60cm without cooltube and around the half with a cooltube so 30 cm so if you adjust the reflector height to keep that distance then the stretch will be limited. But like Athos told you , a blue spectrum will make short plants with short distance between nodes and the red/orange spectrum will lead to stretchy plants. I hope it will help you 😁👍