PLEASE HELP? WHAT COULD THIS BE ON MY PHAL?

[Wynn Dee13]

Hello- I went to water my Phalaenopsis amboinensis var flava today and found that it has some new brownish purple blemishes on it's newest mature leaf. It's other leaves including the new one it is growing do not have these marks. Could it be cold damage? My grow room got kind of cold for a couple nights this last week. None of my other plants have had problems with the cold though. It looks like it is spreading on the underside of the leaf (3rd pic). The whitish spots on the underside of the leaf are old and look like some kind of mechanical damage. I'm worried about the other spots. Any opinions on what it is and what I should do to treat it would be appreciated! Thanks! Here are some pictures:

[isurus79]

Hmmm, if its not mechanical damage, I would say its cold damage from wet leaves left overnight.

[lepetitmartien]

Mhmm fungus or bacteria.

Cut first, talk later.
Put cinnamon powder on the cut, it'll keep fungus and bacterias away.

As it's rather low on the leaf, remove the whole of it.

[Wynn Dee13]

Thanks guys. I think it is bacterial and I am going to cut the whole leaf off. It can't be cold damage from wet leaves because the plant was completely dry when it got cold in my grow room those few nights. Any more opinions would be great!

[zxyqu]

Looks like an infection. Cut the leaf before it spreads, especially if it seems to be spreading.

[Wynn Dee13]

Originally Posted by zxyqu

Looks like an infection. Cut the leaf before it spreads, especially if it seems to be spreading.

Thanks Jarad! I was hoping you would see my post. The leaf is coming off.

[JKostell]

I try not to let my phals get below 50 deg F. I have definitely gotten frostbite on plants under 45 deg f with a wind chill. The leaf(s) get yellow, mushy and fall off and there are signs of root damage (shrivelling). I've also had some sunburnt leaves from overexposure that get black/blistered patches on them.

[Wynn Dee13]

The temp only dropped to 53 F. The infection was bacterial.