Is it ok to let them eat it or should I remove it from where they can get to it? I blocked the area off for now, but want to know if it has a beneficial aspect to letting they go for it.
That should be just fine. Chickens are pretty decent judges of what's good and what's toxic. That color is everywhere on my land and chickens have been eating it for many years with no problem.
As long as they are free ranging and have many choices out there, chickens do well avoiding bad stuff. If you have them confined and offer only toxic 'goodies', they will figure things out.
Most of us have some toxic plants in areas our birds explore, and they find good stuff and avoid the nightshade, poison hemlock, and other delights out there. Fortunately!
Mary
Good advice so far. Chickens are very good at avoiding toxins. Most natural toxins will have a bad taste anyway. And they can clean up road kill with no problem, a bit of fungus isn't going to hurt them.