So I went ahead and bought some more HC. My plan is to let it grow a little and root for one more week and then fill up the tank.
I noticed that the plants on the right side appear to be browner looking. They haven't really melted except in a few spots but they look more withered where the ones on the left are nice and green. I'm kind of hoping that filling it with water and doing some changes will filter whatever the problem is or at least spread nutrients, light, water, etc. more evenly and maybe resolve it.
Here is a pic so you can see what I mean about the side to side health of the plants.
I'll update when I fill it.