Is this a magnesium deficiency?

Nitrogen deficiency can cause purple stems. Looks like you got a caterpillar too!

I'm using N25 - P10 - K10 fertilizer, so i don't think its nitrogen. Do you think i may be feeding to much nitrogen?( the leaves are normal color not dark green)

Honestly unless the leaves were to be dark green with brown tips(sign of over nute) I'm sure your fine.
Your leaves are light green about half the way through the leaf which signifies nitrogen deficiency.
whats your ph? Nitrogen is only absorbed when the water is at a certain ph.
if your using one solution for nutrients Id suggest getting two different types and alternating them.
certain amounts of nutrients can cancel others out as well. I'm not sure if nitrogen is one of those.
it makes sense that when you added more light the stems turned purple. She's saying she's hungry
just my 2 cents

Other than that the plant looks good!

Plants fine.

Some have purple stem by genetics.

In my reading, (first time grower) purple stems are either genetic or a Phosphorus deficiency. I thought Nitrogen caused either broad yellowing or very dark greens; first time hearing of N making purple. Friedrice?

order any of the base nutrients General hydroponics has, a quart of caliMag a 4oz bottle of floralicious plus and a quart of kool bloom and ditch the 25_10_10. Download the correct feeding chart gh offers for each base nutrient and feed 3/4 waterings and water on the 4th. Its $ well spent I promise.

Greggos88 said:

In my reading, (first time grower) purple stems are either genetic or a Phosphorus deficiency. I thought Nitrogen caused either broad yellowing or very dark greens; first time hearing of N making purple. Friedrice?

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They are sometimes caused by genetics your right on that.
but from my experience when i grew some banana kush a couple years back they started getting purple stems.
banana kush isn't supposed to have purple stems. I found out after plenty of mishaps that it needed more light and nitrogen.
Fixed those two and the plant was fine. A phospurus deficiency works its way from the tip of the leaf back I'm sure.
Nitrogen def works from the inside part of the leaf towards the tip

DannyBlaze said:

Have you grown with this dirt and nutes before?
Do your nutes have a brand name like Miracle Gro?

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This is my first grow, brand names are Schultz and plantprod