If the collards are that old they may have club foot or blackrot or black leg. These are seed and soil borne fungal disease. It will first show up as wilting leaves. If it has been raining a lot or the ground has been staying wet for awhile that could be the problem.
If you have either of those conditions, it could be seed borne and it will stay in the soil for a very long time. Don't plant cabbage family there and make sure you get certified seeds. The Pacific Northwest is under quarantine because of black leg and most of the seeds sold for crucifers come from there.
https://mtvernon.wsu.edu/path_team/Black ... -12-14.pdf
Happy gardening in Hawaii. Gardens are where people grow.