Plant light green uniform at the top

[rikymao]

Hello, any body know if the plant have problem?
https://imageshack.com/i/1xqhahj Because all the new leaf at the top of the plant are light green UNIFORM. (see the 2 photo at link)
Instead the new leaf in the middle are dark green.

More information:
- Plant: white Widow NO auto flower
- Led light 210 W
- Hour 18 light 6 night
- Grow box with fan, 2 square meters (4 plants)
- Ground-mix with bat “shit”
- The plants have 1 month and 2 week (tall all round 35 cm)
- I don’t give extra fertilizers

Thanks

 

[RonSmooth]

As much as I hate to say it (its the go-to diagnosis) it looks like you might be running into a Ca & Mg deficiency.

Light green new growth, inter veinal chlorosis... Mg

Burnt, twisted leaf tips, yellow & brown spots, necrotic patches Ca

You will likely need extra fertilizer. Something more complete than bat shit

 

[firehound]

agreed with ronsmooth. check out oyster shell flour. better than d. limehttp://eurekaspringsorganics.com

 

[rikymao]

Thanks for the answer! I gave BIoBiz and the situation now its better.
Thanks!