What Is My Water Sprite Missing?

Hello everyone! I've had this water sprite now for about four weeks. I have a lot of little floaters that I keep in a sectioned off area in the tank so I can watch them. I have planted a few and I think they are slowly growing. As for my other two bunches, they have been planted since I got them. I trimmed back all the dead growth and I am getting a new sprout or two like every week! Really liking this plant so far, I hope it gets taller though.
But, there is one bunch that has a few leaves turning brown on them. What exactly is going on here? The other bunch is doing great so far, but this one and a few of the smaller ones have this. Does it need root tabs or something? I tried looking up deficiencies but I couldn't figure it out.

Tank info:
20 gallon long
12 nerites, 1 betta
Finnex Stingray LED (on from 8am-8pm)
2 ml of Flourish 3x a week
5 ml of Calcium and Blackwater 3x a week (Kent brand)
DIY CO2
Water changes have been a little wonky lately, schedule has been sporadic but I did do one yesterday of about 30%

The first pic is when I first got them, the second is toady, and the third is the brown area I am talking about. There are like little pin holes too. I looks thin but when I touch it, it doesn't melt or anything.

 

Only thing I can think of is a potassium deficiency. Every other main micro and macro nutrient as well as co2 would be covered with what you are currantly dosing. And the other macronutirnt you aren’t dosing magnesium and phosphorous are very naturally occurring in most water supplies. You may try cutting down on the light for a few hours maybe from 12-8 or 9 hours.

 

Could be a potassium deficiency. Root tabs wouldn’t hurt.

 

I may go buy root tabs later on today. I would get the Seachem Potassium bottle but I really don't want to add another liquid to the stuff I do now.
Why would I turn down the lights for less hours? I thought if you had them on for at least 10 hours then that was good, or if you did that whole turning them on then off during the middle of the day then back on again. Could they possibly be burning or something?

 

I love it when I accidently double post lol

 

The longer you have them on the the more photosynthesis takes place and the faster your limited nutrients are exhausted.

 

the older stems of my water sprite get brown too... I think it's just the old growth. it's the original part of the plant from the lfs. new growth looks great. I noticed the old growth sprouts new plants on its leaves, so likely it's slowly dying. plus the leaves at the top of the tank turn brown and get lots of algae because it's closer to my light. :/

 

So I just got the root tabs, they smell really nice. I'm not 100% sure where exactly to put them. I was thinking about putting one right under the two big bunches and leaving the smaller ones alone.
I also got a 45g Fluval CO2 kit but it was an impulse buy and I'm probably gonna return it tomorrow lol. I really want a paintball set up but Idk...
EDIT: Or maybe go back to Excel now that I don't have Anacharis anymore....so many choices.

 

Alright. Listen guys. You probably don't know this but I am a super indecisive and impulse buyer. I saw some of the same patches on the other bunch, meanwhile the floating ones have nothing on them and I feel like they are producing more leaves. So I have decided to float all of my water sprite. Also going to start using Excel after this month's CO2 runs out.
BUT...my question is....I still have the root tabs and I think I should keep using them since I don't know if I will ever plant these guys again, depends on how long their roots go. Will the tabs actually do anything? Like dissolve into the water over time? If so, do I have to keep them buried or will the snails chew on it and die? I see they have a decently high calcium percentage, so I can imagine that's good for snails.

 

Okay so the root tab has like fallen apart pretty much but it's still in the tank. I've weaned the plants off of CO2 and got them on Excel. The root system is growing like wildfire! The biggest one is almost halfway down my tank. I had to put a airline tubing wall in front of my HOB so it wouldn't get thrown around.
But I have a question...I've heard the root system of water sprite can go crazy when the plant is grown emersed, is this true because they can get to CO2 easier? If so, how can I grow it emersed in my tank? Just lay the leaves on some surface decor and let the roots hang in the water?