Leaves Problem

Hello everyone, this is my first grow. I have a problem with a sativa plant, unfortunately i don't know the strain. At this moment is 55 cm, was healty since 3 days ago when began to grow a strange and thin leaves at top. The plant is under a HPS lamp 400W (18/6 hrs). Im feeding once time a week with 1 teaspoon of guano per 1L of water. Just during the last week i feeded her a little bit more because the old leafs on the bottom were becoming yellow. Thank u for every kind of help. Here the pictures.

Up...please some advice

over-watering? how's humidity?

Looks like heat stress to me...how far is the light from the top?

i dont think its over water....just top of the plant its like this..the humidity go around 35% to 50%.

bkbbudz said:

Looks like heat stress to me...how far is the light from the top?

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the light is 25/30 cm from the top

Bulldozer said:

the light is 25/30 cm from the top

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I am American nd therefore not metric savvy how many inches for my neanderthal brain please...LOL!

10 or 12 inches.......too close, i guess.

Sure looks like heat stress move ypur lights up a lil

scroglodyte said:

10 or 12 inches.......too close, i guess.

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BINGO!! we have a winner! Heat stress it is. Move it back about another 6", again I don't know metrics...sorry

are the roots bound? the pot isnt real big compaired to the size of the plant if they roots are bound it can upset the plant a fair bit.

thanks everyone..i will try to move the lamp...about the roots i dont know..i have to check it..how i can do it?

Bulldozer said:

thanks everyone..i will try to move the lamp...about the roots i dont know..i have to check it..how i can do it?

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most pots have holes at the bottom for drainage you can look under there to see if theirs roots sticking out its an indication youll need to repot her

The roots had reached the bottom. I changed the pot. seems getting better now..thank you