Help cracking on bonnet vents!

[coley500]

Help..I have just noticed some major cracks appearing on nearside bonnet vents. I noticed alittle while ago some paint was starting to come off, now this is like creeping death causing small veins under the paint...I have photos but cannot figure how to get them on here. I want to try to stop there progression any further and then what to do to make good. Cheers.