does anyone know what this is?

little seedling looks sick. I'm not sure if you can tell in the picture but the little leaves are kind of folding over. I'm using a topfeed/DWC hydroponic cab. I'm using a 180 watt UFO LED light that is running on a 20/4 light schedule. My pH level is staying pretty consistent at 6 and my PPM stays at around 61-65. although I added some nutrients so now its up to 91. the temp stays between 79 and 85F and my RH is at around 45. any advice or ideas?

Is it just that one plant? Usually when you see the tips curl like that it's a sign to check your humidity and/or heat. Both of which you'ved checked.

folding of the leaves could be a couple things, depending what you mean.

if you mean they are beacoming very ridgey, (like the green arching up between the little secondary viens on the leaf) that is usually over watering or ph , speaking of witch you ph seems a bit low to me'

if you mean they are curving downward. that mean your light ratio is unbalanced. by this i mean, plant can use capillary action to shape themselves for optimum light absorption.
the direction the leaves curve is determined by the direction and intensity of light recieved. if the light recieved from the underside of the leaf isnt signifiganly lower than the light recieved from the top the leaf begins to curve.
the underside of leaves dont like light.

two options increase how much light is recieved from the top.
or reduce light from bottom (a BIG sheet of black construction paper would reduce your reflectivity from the bottom)
whatever u use make sure its water resistant and non reflective.

have fun S A

they are kind of curving downward, also they're a little darker in color. Sorry the picture isn't that great but you can kind of see it.... so the lid to my reservoir has 14 holes. I only used 8 so I covered the others with reflective tape. from what you said I guess this is a bad idea since the under side of leaves don't like light, right?

So is it 1 out of 8 that has this problem? And how intense/close is your light? What kind of light? Looks like LED from the picture.

it is a 180 watt LED light. I'm keeping it about 5 inches from the top of the plants right now