black leaf tips...any ideas?

[scinerd3000]

Heres where im at right now. My leaves including the new ones have been curling up on me. The plant seems to be growing fine although the Mt.Hood is waaaay behind my Cascades which are now 8ft and counting. I dont believe they are underwatered so i cant figure out why the leaves are curling. Probably close to 70% of them. Ideas?

 

[HoppyDaze]

My nugget plant is doing the same thing...I would really like to know what is causing this?

 

[scinerd3000]

Its getting worse...any ideas?

Im really worried because the leaves also curls around the growth tip...