Catt leaf tips turning yellow/brown?

[Orchidreamer]

I recently got a catt and several of its leaves are turning yellow/brown at the tips. Some leaf tips have only brown, others are only yellow, while the rest are brown with a bit of yellow. Both newer and older leaves are affected. Is this anything to worry about? Do you think it's some sort of disease? What should I do? The plant's otherwise healthy. It's 65 deg F, 40% humidity. My other catts don't show these symptoms.

Edit: Yikes, I just noticed one leaf has a 3" yellowish oval-shaped area with lots of brown spots dotted within the yellow area. A fungus problem?

Another catt that I got recently has a leaf that's yellowing. The leaf is the oldest leaf. I gave it a strong-ish dose of superthrive earlier, and I don't know if that's causing problems or something.

thanks

[Ray]

Could be either fungal or bacterial.

I would cut off all of the affected parts - with about a 1/2" margin of good tissue - and dunk it in 2 tsp/gal Physan.