My phalaenopsis orchids are turning yellow and dying suddenly

[Supernic]

Hi,

I have purchased several orchids in the last 7 months. Since February, the climate in my town has turned very hot and dry. I water the orchids every alternate day. While the cattelya, dendrobium and other orchids are healthy and growing new shoots, my phalaenopsis leaves are suddenly turning yellow, the roots are dring and the plants die within a week. I have checked that there is no root rot. I am growing them indoors and have installed led lights along with sunlight. Today I placed a humidifier too.

Please check the photos and advise what is wrong.

Thanks