With medium light, injected CO2, and root and dry ferts, blyxa japonica did fine moving into my hi-tech tank after arriving. I put a couple stems into my low-light, low-tech tank for an experiment, and those stems started yellowing after a few weeks, so I tossed them.
Remember, blyxa grows to about 4 inches ...and stops. Of all the plants i've grown over the past 6 months or so, blyxa is one of the prettiest, and yet least impressive. Aside from pushing itself out of the substrate and occasionally growing new stem systems, blyxa japonica is fairly predictable and not necessitating any maintenance.
They do look pretty bad. I would leave them in the tank for a few days and keep a close eye on them. If they start to melt and die off, then remove them. I have had Blyxa bounce back from some real bad conditions, but its 50/50.