Why do the tips burn?

[Myka]

Another speculation is that increased alkalinity causes the coral the lay down skeleton quicker, and the skin cannot develop as quickly due to the low nutrients, so essentially the skeleton bursts out the end. People come to this conclusion from seeing pale tips in Acros that are growing quickly. I'm not sure I buy this theory. My Acros will get tip burn if alk hits about 8.5 dKH, so according to this theory, my Acros get a sudden growth spurt for like 2 days??? I don't know, I don't buy it. Plus, you will see alk burn on Acros that have dark skin which indicates that the Acros is getting lots of nutrients (even if the water column nutrients are low).