A very common problem for the peace lily. It can be an indication that something is bothering your plant
This usually means your plant is thirsty. It can also mean that water isn't reaching the roots.
This can happen for a variety of reasons such as mineral build-up, overwatering and underwatering.
Common causes include leaf burn, cold exposure, underwatering and bacteria/ fungus infections.
This can happen because of either overwatering, underwatering or lack of nutrients.
Usually not a cause for concern. You should also check the leaves for any possible issues.
Peace lily flowers turning green after having been white before is usually just part of the normal peace lily flower life cycle.