Interesting problem late in flowering (Pics)

I have a Big Bud plant flowering since 1/06/09 in ocean forest soil/perlite mix in 3 1/2 gal pots with half strength fox farms nutes every other watering. I water about once a week, I let the plants start to get droopy before I water thoroughly (about 1/2 gallon per plant).

Temp in the room is around 72 +/- 5 degrees. humidity is around 25% constant.

Everything is going great until I noticed some of the leaves start to curl a bit upwards near the top of the plant. Looking at it closer I noticed that some of the main cola dried out. There is a chunk of it that is completely dried out and yellow to the core.

Anyone seen this before or have any idea what it could be? All the rest of the plant and even the rest of that main cola bud is doing great and showing no problems.

I tried to get some pics, but everything looks yellow with HPS








Any help would be appreciated. I'm affraid of this stuff spreading and drying my whole bud to the stalk!

too close to light? could be 75 degrees in room but 100 where that bud is

Hard to say really on those pics alone.... close up of leaf and stem would be good...

Sounds like heat burn to me too. Do any of the curled leaves look bleached? More whiteish than yellow?

Thanks for the responses everyone!

Hmm..I thought it was a heat issue at first too, but holding my hand at the same position in regard to the bulb felt ok, it was warm but wouldn't call it hot. I'll try to get a better shot with the HPS off. I guess it kinda has to be a heat issue, I just can't think of anything else that would cause that. weird.