It looks like a red plant, and to my knowledge red plants need lots of iron. They also need decent lighting.
I have 2 2100 lumen leds on my 125 gallon. I feel that shoukd be enough. Also dose the tank with flourish
Looks like a red hygro. I’d say you don’t have enough lighting. Lumens is an older measurement and if I remember your looking for at least 3500 lumen. 2 2100 is still only 2100. Look into a finnex HCL either one 48” or 2 36”. Guessing your tank is 6’. Another good light for half the price is the vivagrow 24/7. It’s giving 10k which is bright. The finnex is 6k.
Red plants are hard to grow you usually need co2 for them to flourish. With the above light that plant will grow but probably turn green. Top may be red.