Yellow spotting on leaves?

[Lucinda Brown]

Anybody know about the cause of yellow spotting on leaves? I don't think it's iron deficency because that's usually yellowing of the whole leaf or plant. Could it be cold water? Or some chemical like chlorine in the water? I'm only getting it on some of my greenhouse plants,none that I grow in our sunroom,same water both places but no way to adjust the temp of the greenhouse water.Mostly on paphiopedilums and a few denrobium nobiles.Any of you experts know about this and have any hints to correct it or at least keep it from continiung? I would greatly appreciate some help!:

We need a better description of the yellow spotting. Are the spots large, and blotchy? If so, that might be a case of sunburn. With the nobile, it may simply be that type of den is deciduous and lose their leaves this time of year. Chlorine doesn't seem to bother orchids. Although I know it's not good, I'm not sure what cold water does to the leaves. Are the spots the size of a dime? Tiny? Do the spots make the leaf pitted? Please try to give us more information.

[jerrymeola]

First the Nobile dens will all turn yellow spotted and the leaves will fall off. Their normal growing pattern is to lose every leaf every year. They flower best on bare canes.

The Paphs also yellow and lose leaves easily. Mostly because they are more delicate. If it is growth that has flowered before then everything is normal. Only when new growth is dying should you be concerned.

[Lucinda Brown]

They are just small yellow splotching. Definetly not dime size. Mainly on the new growth of the paphiopedilums. Older growth on nobiles. I figured lack of something or cold water? Seems to be getting better though on the paph.