Thin stems

I have a Sour Kush going now that had a rocky start. Purchased at a VT dispensary as a clone that appeared to be dry and root bound in the 4 inch container, started it off in a 2x2 DIY tent with a 150W HPS bulb (which worked fine with my 1st grow of Cash Crop) and outgrew the area about a month in so I tied down a few of the stems. Purchased a 3x3x6 tent and now space in not an issue, but some of the stems are bent over b/c of the weight of the bud on the ends (not complaining about that !) . What may have caused this , and can I just tie the weak stems to stronger ones ? Thanks

Welcome to RIU! Many here would love to offer some help to you. It would help a lot if we had a picture or two, to go by. And it works way better if you could take said pictures with the grow lights off. Just take the pics right before the lights come on.

The cause of your issue is hard to diagnose without seeing the plant. But being it was under a 150w light, I would guess it was stretching to reach more light.

As to tying the bending branches to other branches- I would not do that. If the branches in question are already bending under the weight it may cause the others to bend as well. Since you are in a tent now, I would use something tied to the ceiling to support them. When I have buds get too heavy I tie an 18 inch (or so) long piece of solid 12ga insulated wire to a string or elastic string suspended from the ceiling. Then I bend the wire into a wide hook and use it to support them like these two in the front. The wide hook makes it easier to remove when you need too. And the long line will let the branch move with the breeze of an oscillating fan.
If you don't have a fan moving air around them you should, as the movement helps to strengthen the plant. Good luck. And post a picture to see if anyone can offer more help.

lots of things can make them grow that way, genetics, being too far from the light, not having enough light, even repotting at the wrong time. if you like the plant and took clones off of it, i'd make sure to keep them close to the light, (obviously not close enough to burn, but as close as you can get and not...) and maybe add a little silica. it's usually not needed in plants grown in soil, but some strains with weak branches can benefit from it, even in soil. cold water kelp extract contains a pgr (plant growth regulator..in this case, cytokinin) that promotes short bushy growth, so adding a little to each watering of a stretchy strain usually will help a little.

Thank you both for your replies, any info is very much appreciated. I will post photos latter today. One question I have for JimmiP is about tying the stems from the ceiling, do you use the "hook" for easy removal so that you may rotate the plant, which I do just about every time I water/feed ? Or is rotation a waste of time

A trellis is handy for holding up your buds, for future grows consider setting up a trellis rig.