Seedling problems

[darcey]

Hi,

This is my first grow in 7 years so I'm a bit rusty and might be jumping the gun...

My seedlings are Paradise Seeds Sensi Star (fem) and are about 18 days old. They were popped in a shot glass of water and transferred to rockwool cube after a root appeared. They then spent about a week under a dual tube 40W fluro before being moved to a 250w HPS 3 days ago.

My problem is one of the seedlings has developed a very thin and weak stem, to the point it can't hold itself up. It was doing fine then one day just fell over! I propped it and it seems to still be growing but I'm worried it might be a dud. As you can see from the pics the other seedling seems to be going strong

Does anyone know what could cause this “weak stem”? Should I be worried or just let it go and see what happens?

Also after transferring the seedlings to the 250W HPS (not ideal I know but my fluro died) the “good” seedling’s leaves seem to be bending down…Could this be due to the light difference (HPS vs Fluro)?

Thanks


Funny stem

Same again

Good Seedling under fluro

Good seedling after 3 days HPS

 

[darcey]

More info about the grow

What STRAIN are you growing?: Paraside Seeds Sensi Star
What was the establishing technique? (seed or clone?): Feminized Seed
What is the age of your plants?: 18 Days
How Tall are the plants?: 4 inches
What PHASE are the plants in?: Seedling
What Technique are you using? (SOG, SCROG etc): Nothing, still seedlings
What size pots are you using?: 100mm Net Pot
What substrate/medium are you using?: Hydrotron (clay balls)
What Nutrient's are you using?: 1/4 strength GrowRite for the last 8 days
What size bulb are you using?: 250w HPS
What is the distance to the canopy?: 2 feet
What is your RH Factor? (Relative Humidity): NA
What is the canopy temperature? NA
What is the current Air Flow? (cfm etc.): Fans rated at 254CFM
Is the fan blowing directly at plants? No
Has plant been recently pruned, cloned or pinched? No
Have any pest chemicals been used? If so what and when?: None
Are plant's infected with pest's?: No

 

[dr-dank]

I think you would be better off with a compact floro that is much closer to the plants. They look low-light stretched to me. Yes, you can grow seedlings under an HPS, but its not effecent and can lead to issues of stretch when too far away, or burn when too close.

HTHs

 

[MEDI-EVIL]

put a small stick in the pot to prop it up..

 

[darcey]

Cheers for the info guys...Still at a loss why the stem is so thin

I got some new fluro tubes today and moved them back under...When moving them i noticed the good seedling now has a yellow spot on one of the leaves...Thinking something nute based I flushed the media, dumped the 1/4 strength nute solution and replaced it with plain water.

See what happens in the next couple of days...

thanks again