JR_Roosa,
Nice looking coastal redwood! Love the picture with the suspect next to the crime also.
About the browning on the tips of some leaves:
Please look at this thread that has to do with my Dawn Redwood and some advice from other members:
http://forum.bonsaitalk.com/showthread.php?t=17635
My conclusion from what I have heard from others and seen for my self is that since the tree has a lot of folliage and not much roots to support it (inside a pot), the fluid reserves are low, and when temperatures go higher and humidity lower, the tree will suck more water and if it doesn't find enough then he browning will happen. I have to keep this tree very well watered and on a rigid schedule to minimize browning of the leaves; your dripping system is most likely a reasonable solution. Just make sure that you get the water into the pot, and not just misted on the leaves. I am letting my redwood have a lot of folliage because I want the trunk to develop faster.
About the black leaves:
This is just a guess: Maybe the leaves are to touching the soil and carrying up something undesirable like bacteria or fungus. I would just trim anything that touches the soil to make sure nothing climbs up by the leafs. If only black leaves are on the lower branches then this might be the case. Simply cut anything that comes into contact with the soil and/or use some kind of support so that nothing touches the bottom.
Regards