What fertilizer are you using?

I doubt that the brown spots are caused by the grow light. They might be caused by salt built up from fertilizer or from sort of spray. Have you sprayed it with anything?

Try to flush the soil with lots of water. As Vladimir pointed out, it might be salt built up.

I haven't sprayed it with anything, but I'll try and flush the soil out and see if that helps. Thanks!

I used a general purpose Miracle Gro fertilizer diluted to about 1/4 to see if the chelated iron would help.

Thanks a bunch! I'll report back in a few weeks to see if anything changes.

ADD a table spoon of vinegar to a gallon of feed water. Spray with a vegetable fungicide per products instructions. Kumquats have a very hard time getting started, I have a 96% seedling dya off rate with Kumquats compared to about 10% with none kumquat citrus seeds.

Steve

Thanks! This is just to protect them from disease?

And yeah, I definitely believe it. It's been over half a year since I germinated them from the fruits I bought and they're still only about 2 inches tall at most and have difficulty holding on to new growth.

16 hours of light minimum using a day light CFL/LED bulb.

Meiwa · More Info

Meiwa kumquat seedlings 1-15-2017

Greenhouse and bucket lights · More Info

Meiwa kumquat seedlinf from 2013/20/14

Greenhouse and bucket lights · More Info

fig tree in bucket light

Greenhouse and bucket lights · More Info

Meiwa · More Info

Meiwa seedlings gets bucket light on top.

They grow very fast after they have branched out and are about 2 feet tall,

Seedling Meiwa 1 year 9 months 10 days old. 16 hours of light is needed for kumquat growth.

Typical kumquat root is very short compared to tree length.

Steve

I accidentally sunburned some seedlings and the damage didn't look like that. And I thought fertilizer burn usually affects the leaf tip.

Miracle grow doesn't have chelated iron, does it?? Or did you add it?

It is good to use chelated iron with micros.

It looks like the box I have lists chelated iron (0.5%) as an ingredient, weirdly enough! I'm hoping that it's enough to help them out.

I've already flushed out their soil so hopefully the new growth will turn out okay.

Another thing I found is mealy bugs attacking the one pictured above, and I'm wondering if they could be a factor in the spotting somehow.

Remember lots of light, 16 hours per day

These meiwa seedlings sprouted mid December.

16 hours of light inside a bucket light.

Steve