Magnesium Deficiency?

Hey everyone, been looking at my plants lately and they seem to be yellowing a little like a magnesium deficiency, got some pics for you all to see.

Pic 1 is my 3 week old plant but I think it is also overwatered.

Pic 2 is my 8 week old plant with clear yellowing in the middle.

Pic 3 is my other 8 week old plant which seems to be affected the worst.

Pic 4 is a close up and comparision of the 2 different leaves, The yellowing seems to be only on the new leaf sets.

Another possibility is it heat stress?

Please help ASAP thanks

Or is it Iron deficiency lol?

That.loks.normal.to.me.an.definately.not.a.Mg.def. .Pic.1.is.way.overwatred(I.had.this.problem.with.a .few.clones.once..The.new.growth.is.usually.lighte r.green.till.the.leaf.opens.and.the.light.activate s.the.chlorophyll..When.they.get.bigger.you'll.not ice.that.leaves.and.branchs.in.the.shade.keep.the. light.green.color.til.they.are.exposed.to.light..

Stop.overwatering!

what kind of water are you using and how old are your plants?

If your using R/o water, then you need to add some calmag+