Base of leaves yellowing and falling off when introduced to climate controlled enviro

[OzPhal]

Hi everybody,

I've recently introduced my Phalaenopsis seedlings to a climate controlled growth chamber where i control lighting, humidity, temperature, light cycle, air movement etc. In their previous environment they were receiving less than optimum light, temp was less than 20oC as we're going in to winter and the humidity was still up around 70% with high air movement. In their new environment they're experiencing a stable temperature and humidity and a 12hr on 12hr off light cycle - lighting was initially around 1,320 ft candles but i've dropped this back to 660 ft candles and will steadily increase to the 1,320 ft candles. I initially had the temperature at 28oC but have since reduced this to 25oC as the shock change from their previous environment to their new one would have been over a 10oC difference. In any case on some of the seedlings the very bottom leaves on the plants are yellowing at the base and then dropping off. Is that normal? Is it simply an adjustment to the new climate? Also, one of the leaves on a P. bellina copped a little damage in the move - it appears that the damage has spread over the leaf a little - it's now stopped though. Should i leave the leaf on there or remove the damaged section? I've attached some pictures of the yellowed leaf, the damaged leaf with a black spot forming and also an overall picture of the setup that i have. I have in there:

* P. bellina
* P. schilleriana
* P. venosa
* P. Brother Peter Star
* P. Yu Pin Pearl
* Dtps. Kenneth Schubert

[OzPhal]

31 people have read but no one has ever come across this before?

[Zoi2]

You've got a really nice set up.
I've never grown anything in a climate controlled area so don't know much about the pros and cons. Your yellow leaf could be natural die back but since it's on a seedling I would think maybe stress. The black spot on the leaf looks bacterial/fungual to me. You may have had a drop of water on that leaf. How is your air circulation?
Joann

[Eyebabe]

Your first leaf looks like crown rot type infection (pseudomonas).
I think the yellow leaf most likely has the same.
The high humidity will support the infection if present despite good airflow.
Infections occur despite the best of conditions and I would perform a treatment with Phyton 27 and use some dilute physan in the water as well.
Certainly, taking care that the concentrations won't harm the seedlings.
I hope this is of some help

[OzPhal]

Thanks everyone, i appreciate your help... I actually did some further reading yesterday and found that the Phals prefer a day time/night time temperature... so i've modified the growth chamber to be 28oC during the day and 18oC at night! the higher temp during their night phase i think would have been causing some stress... I'll get hold of some physan - thanks for your help