Cabombas are dying/Sagittarias not growing
Hello! I'm new here. I've had a little bit of experience with some types of fish and plants but I still have a lot to learn.
I have had my "Green" Cabomba plants since I got my 40gal tank in September. They were growing very fast and looked very green for a couple months. About two months ago, most of their leaves started dying off, they started growing extremely slowly, and their stems keep rotting, breaking, and getting uprooted.
I also have three Dwarf Sagittarias that I've had since last month. When I first got them, their leaves quickly started dying because my water conditions were very different from the pet store's. A friend of mine (a fish and reptile expert from a pet store) suggested I cut all the leaves off so they will grow back when they have adapted to my water conditions. It's been a month and their leaves have grown about a fourth to a half of an inch in length. I thought they would grow faster?
Here's a bit about my tank:
-Ammonia level: 0
-Nitrite level: 0
-Nitrate level: 0
-Temperature: 75 F
-Tank size: 40 gallon breeder
-The temperature is always kept at exactly 75 degrees.
-I use liquid fertilizer
-I have two fluorescent bulbs (75 watts each; 1,170 lumens each; 6,500 K each) and one fluorescent tube (I think around 20 watts but I'm not sure...)
Is there anything I can do to help them get healthier? Any suggestions?