too much light?

so i read somewhere on this forum that too much light cud be a bad thing.
now my veggie grow box is verry small 29"H 16"w and 21"d i have 2 70w and 1 65w bulb all 6400k is this too much light for this area?
reason for me askin is from germination my plants would grow fine and get to about 4 weeks then start drying out. what i notice is once the plant gets enuff leaves they start turning yellow and drying out.

i raised the lights which is bout about a foot away from the plants now
i added more fans to circulate the air
i removed half the door cover for even more circulation so i am not sure if temp is a prob my thermometer has not arrived yet
also put all my intake and exhaust to run 24\7
also wit my current grow i started addin some nutes *local brand no brand named stuff* n20 p20 k20
i grow in soil and run 18\6 lights
my water ph is about 6-6.5 *i dont have a meter i use a solution that changes color wen u add it too the water*
i grow in soil and have the plants in small pots maybe half gallon i think

any advice i will be great full for

first pic is of my lights 205watts in all
2nd pic 2 younger plants comin up with only a few leaves
3rd the grow area
the last 3 are of a plant that started gettin dry as the leaves came in
sorry for crappy pics would try to get better ones later

75 watts per square foot is the limit and even that amount can be bad so most people use 50w per square foot,But i wouldn't really go by that when using cfls so about 100W per square foot should be good.Yellowing that early means N deficiency and at night make sure your intake doesn't make it too cold that can also cause yellowing but mainly in new growth.Growing in a half gallon pot is fine for your space and it should keep the plant less than 2ft most likely 1-1 1/2 feet tall MAX unless its stretching,but even if it does grow as tall i suggest lst (tie it down)

I'm not sure there's such a thing as too much lite, just a heat issue and color spectrum. temp is important obviously, get a thermometer ASAP. Your plants are a bit young to have nutes, watch your ppms. most soils have nutes in them so don't overnute, let the plant use up what's in the soil first.

Optimal lighting using HPS/Metal Halide is about 75 watts per square foot, but this assumes perfectly even light distribution. Sometimes that isn't the case, and you need to boost overall light in the middle so the sides aren't too dim.

With fluorescent lighting, the lights are typically about 20-30% less efficient, and the light spectrum isn't as favorable. If you're using CFLs, on top of both of the above, the reflectors are typically not as good, too, so you end up wasting a good bit of the light output. So depending on what type of bulbs you're running, and how they are reflected, "optimal" lighting may be as high as DOUBLE the above.

Until you get to near double the optimal lighting you aren't really going to hurt the plant, you're just not going to see any increase in growth (well, unless you're also supplementing CO2).

The main problems with overlighting are that you generate lots of unnecessary waste heat and are wasting energy.

Anyway, your 16x21" cab is 2.3 square feet. 205 watts of fluorescent lighting for that space sounds just about perfect to me.

The main thing is, 200 watts is a HUGE amount of heat for a small cab, I'd be concerned about overheating.

I don't know why you're waiting to get a thermometer in the mail, when you can buy a functional (if not fancy) small thermometer at Walmart for literally one dollar or any hardware store for at most a few bucks.

If you're aggressively ventilating to control temperatures, you may also be drying out the plants. How often are you watering? Does the soil get dry?

Leaves turning yellow is typically a sign of nitrogen deficiency. With some strains, during normal growth, its OK for the plant to shed off its bottom "new" leaves (which will turn yellow) as it gets taller. But you NEVER want most of the leaves or the top growth to be yellow.

From your description (plants turning yellow and leaves drying out once they get to a decent size) it sounds to me like your plants are overheating and/or not getting enough water.

Bigger pots may also help here since they allow for more water reserve.

just an update, i got my thermometer and i also got AC around the same time, with the ac on 23 degrees C my grow area is around 73 lights off and 85 lights on, so i believe that without this ac my room cud have been well over 100 degrees, so heat was my problem after all. the new seeds i popped are lookin alot healthier than the previous plants wit alot more roots too. ill take some pics later on as the plants get bigger

DeeTee said:

I'm not sure there's such a thing as too much lite, just a heat issue and color spectrum. temp is important obviously, get a thermometer ASAP. Your plants are a bit young to have nutes, watch your ppms. most soils have nutes in them so don't overnute, let the plant use up what's in the soil first.

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Believe it or not but it is possible to give you plants too much light. A seedling would probably be the most susceptible to this.

Sorry to dig up an old thread, it's neater than starting a new one.
I have a newly sprouted seedling and I turned on my light for the first time, I'm now wondering the same thing the OP was.
I'm using a softbox with 2 x 28w (40w equivalent) flourescent spiral bulbs at 5500k.
The box does a very good job at evenly distributing the light and I have it about 50-60cm away from the plant.
Good amount of light or should I turn off one of the bulbs?

Well IMO if the plant is at least 3days outta dirt they love the bright lights. I got 30watt cool cfl bulbs literally like 2inches from touching my lil ones n they love it. Are u over feeding or over watering? I wouldn't add nutrition so early as most soils provide enough nutrition for at least 30day.