What is this?

[zappaa]

Hi!

I have this Little plants, from good feminized seeds.
They are about 6 weeks old.
I gave them just a bit of calcium.

This happened. Do you know what is this?

 

[warble]

I'm thinking you could use some epsom salt.

 

[go go kid]

magnesium and calcium should be given at the same time. they allow the plant to photosynthasize propperly hope that helps

 

[GenericEnigma]

Hi!

I have this Little plants, from good feminized seeds.
They are about 6 weeks old.
I gave them just a bit of calcium.

This happened. Do you know what is this?

View attachment 5309958

Lots of possibilities. You would need to provide a lot more information to get proper help on this one. Another picture or two could help, especially of the top.

 

[Phytoplankton]

OK, for 6 weeks it is very small. As said, we need more info on what you're growing in, your watering habit (looks overwatered), the nute brand(s) you're using, and how much, how often. The leaves look pretty dark green, so I doubt it's a N issue, unless there's too much N, then it can interfere with Ca/Mg uptake. Once you give us more info we'll be better able to offer help.