Skinny Stem On Sprout

what would cause this?
seedling about 3-4days old, stem is really skinny in middle on 2 plants but other plant is normal, same seeds but the normal one is in straight perlite and the 2 with skinny stem are in coir-peat and perlite.
no nutes
25-30c
50-60%rh
125w cfl 4" above
any ideas?
this one fell over so i ripped it and took pic

Usually when sprouts stretch like that they aret getting enough light move your bulb closer if possible hope this helps.

oh yes, agreed, move the lights closer.

its not stretched its skinny. other one is same height but its not skinny.

what are the size of pots that you have them in?

Get a breeze blowing on them, like a tower fan from X-mart put on low and oscillating, sure you already knew this, but just incase will make ure stems nice and thick!

pots are about 350ml, not a prob at this stage
have fan

thought maybe its the soil but ph seems ok

your issue is defiantly light. seen this before and experienced it before. just move light closer to sprouts, probably gunna have to prop her up too cause she is VERY stretched out

light and a small breeze on them will fix this problem. It almost looks pinched did you pinch it at all when you ripped it or is that how it was?

the bit that looks pinched is what im talking about. the middle of the stem is really skinny.
light is fine, its not a small household cfl its a 125w, around 8000lm.
theyre not stretched. the one that doesnt have the skinny bit is the same size, the other one that does is still standing and stem looks a bit fatter today but its still got the skinnier bit in the middle.

Can you measure it with a ruler and tell us how tall it is? It looks stretched to me. You said the one in the pic fell over? That is usually a sign of the lights being to far away.

1 inch
its fell over because it had a skinny bit in the middle of the stem
the 125w puts down more light at a foot away than a 25w will at an inch.