node spacing jumped up after switching to 400w mh

It seems like the node spacing has just about doubled after switching from cfl/t5's to 400w mh. I gained about 80 watts but it seems like they are stretching like crazy now. The light is air cooled and is only about 5-6 inches above the tops

is this something i should stress or is it not a big deal/unavoidable?

is close to 3.75-4 inches between nodes

That seems like a lot of stretch for just changing to a different veg light. Is the bulb old? As they age the bulb color temp will shift and could be causing it. Other things to check are if your temps jumped when you switched, make sure you're still on the same time schedule, they may be requiring more nutes or more frequent watering due to the switch. Try to only change one variable at a time until you know what's causing the problem.

the bulb is brand new, the temps are lower except in the immediate bulb area going to pull two of the plants out- i read over crouding could lead to the plants "fighting" to grow over each other (its pretty tight in there right now)

i think the light was too close and they were fighting over light, i backed the light up to about 8-10 inches over the tops for a more even spread and it appears the nodes are back down to 1'' roughly apart

(i was trying to get the bulb as close as possible for intensity)

for a 400 watt mh you could be running 2 to 3 feet away and would lower the temps considerably and having a fan moving over the canopy to exchange air so heat cannot build up. the stretching is likely from heat being so close.

I agree , the change from cfl to 400mh would have made the the temps warmer and made the plants stretch, raise the light to 24 ". Try to get a cooltube over the light ,not just an air cooled fan in the light, and you can move the plants closer again.

glann said:

i think the light was too close and they were fighting over light, i backed the light up to about 8-10 inches over the tops for a more even spread and it appears the nodes are back down to 1'' roughly apart

(i was trying to get the bulb as close as possible for intensity)

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keep it that way bro, the closer, the better, unless like you said, you have too many plants to have it that close for a even footprint, i keep my lights as close as possible, and if a scraggler doesnt get the direct footprint, well, rearrange your plants every few days , make sure you have good air flow if you got the lights close as fuck though