Looks like dust has gotten into the DLP chamber.
Have you modified your projector lens by spacing it out? If so, the electrical tape method of sealing the gap is not sufficient for keeping dust out. Generally a high heat silicon sponge gasket is needed for this purpose.
There are methods for removing the dust. Google “cleaning dust from camera sensor” to get an idea.
Sometimes dust defects will not adversely affect the build since they tend to be out of focus, but you will not know until you test.