So I planted some bacopa monnieri 2 days ago and the bottom leaves seem to be melting (turning light brown/translucent) is this normal for newly planted bacopa?
Not in my experience. What I would do is see if it starts to improve or get worse. Make sure your water and/or substrate has enough nutrients. You may also wish to look up an aquarium plant deficiencies chart or a youtube video on that. I find Aquarium Co-Op's video on the topic to be helpful if you are new to the idea.
What kind of lighting are you running?
I'm having similar issues, where you able to recover them
I have had them for a couple of months now. All of them lost their bottom third of the leaves. That is normal. What you want to see is new growth in the top after a month or so. You can cut off the tops and plant them again. You can even leave the bare stem and it will grow leaves
The first pic you can see how they lost their leaves. They still grew an inch.
Second where I trimmed them and replanted. Sometimes you will see roots pop out mid way. Cut under the node.
The last pic I found the top of one floating. So I re planted.
I'm running smart led lights nothing special. Dose with all in one fert. And patience they will grow.