Newbie mistake?

I really liked the Saggitaria I found, so I bought without thinking. It's only been a few days and already it's turning brown at the tips. Water quality or lighting?

Admittedly, I only have LED lighting and I knew better than to get this before I had a new hood & the right florescent bulbs.
Also, I haven't done anything special to supplement the water yet. Not sure if I need iron or the under-substrate tabs. I clearly don't know what I'm doing lol.
I'm surprised that I'm seeing brown so soon through.

Testing is:
Ammonia - 0
Nitrate - 0
Nitrite - 10ppm
pH - 7.8 (might be too much)
temp 76*

Love to see some response on this. I haven't much luck with these plants either.

I hope we get some help.
I just came back from the store with some Flourish plant vitamins, so we'll see if that helps.

Fertilizer hasn't helped me, I can keep them alive but they just never do well. I can grow Java fern, jungle vals, spiral vals, almost any Echinodorus type, but Sags just survive. Tried tabs, liquids (including Flourish), the iron supplement helped all my plants except the Sags. I actually haven't had much luck with Crypts either.

My water is very soft, I sometimes wonder if it was a bit harder the plants might find something that is currently missing.

By the way, extra lighting didn't help me either.

The leaf that is turning brown looks like a terrestrial leaf that is dying due to the plant being put underwater.,

The main reasons aquatic plant leaves turn brown is:
1) Sudden temperature changes, where they get taken from a coldwater pond and put in a tropical tank.
2) Lack of light, usually happens when taken from a pond with full sunlight and put in an aquarium with low light.
3) garden or terrestrial plants being submerged in water and drowning.

Modern LED light units are fine and most provide brighter light and better quality light than fluorescent globes. LEDs also last a lot longer than fluorescent.

I keep reading that LED doesn't have the right spectrum for plants, so I almost spent $50 on a new hood today. I don't want to spend $50 on a new hood but I will if I hafta. I think my tank is actually brighter than the one it was in. It was one large clump, fully submerged and the clerk gently separated it into 5 shoots (so she could charge me $$ x 5). I put them in my tank that evening after rinsing in tap water to potentially remove any pests. I didn't know that I wasn't supposed to bury the base of the leaves until the next day, so I gently tugged on them until the bases were above the rocks. A recent water test said my well water's Calculated Hardness is 27ppm = "slightly hard". There's another bunch on the other side of the tank that looks fine. If I look at them long enough I can convince myself that they've lightened up a little, but not enough to be certain. (attached)


Just found these -

• "Because Dwarf Sagittaria are root feeders, they need fertilizer to better absorb nutrients sourced in the water column. You can offer both a substrate and an aquarium fertilizer. They need a nutrient-rich substrate, as they are prone to iron deficiency. One signal of a lack of iron is yellow or discolored leaves"
  

  Dwarf Sagittaria Care Guide (Sagittaria subulata)

  Consider adding the Dwarf Sagittaria to your acquascaping; be fully informed by delving into our care guide to find out if this aqua plant will suit your needs.

  www.fishkeepingworld.com
• "It should be planted in a nutrient rich substrate, or the water column should be regularly fertilized." https://aquariumtidings.com/dwarf-sagittaria/
• Leaves yellowing from the tip then become transparent = Iron deficiency https://www.ratemyfishtank.com/blog/diagnosing-problems-with-aquarium-plants
• "when you prepare to plant your Dwarf, make sure you put plenty of nutrients in the gravel. These plants need a lot of fertilizer to grow. And if they don’t have iron they will wilt and die. When you plant your dwarf, plant it gently, but cover the roots. A little bit of care is all this plant needs to thrive!"
  

  Top 10 Aquarium Plants That Grow in Gravel (With Pictures)

  You might be wondering whether your tank plants can be grown buried in a gravel substrate. In truth, this depends on what species of plant you have. Generally, gravel is a great material to grow

  aquariumgenius.com

Ok, well that explains it... I've added liquid iron to the water, but it needs the substrate tabs. Hopefully I can keep it from getting too bad before I nurse it back.
*sigh* Back to the fish store!

Sagittaria tend to do best in cool water and often struggles in Tropical tanks

You don't need a substrate fertiliser or root tablets for Sagittaria. A liquid aquarium plant fertiliser is fine for them.

Modern LED light units are fine for plants and most people growing plants on the forum use LED light units. Some people still use fluorescent globes but modern LEDs are fine for plants.

Thank you everyone!!