Fertilizer problem

[SheilaJ]

I'm not a very frequent fertilizer, but when I do get around to it, a couple of orchids (not always the same ones either) usually rebel. Typically one of my phals will drop its flowers within a day or two, and one or two of my terrestrials (phaius and spathoglottis) will get really bad brown tips on the leaves.

I'm using Jack's liquid fertilizer at the recommended dose, and I water first so I don't burn the roots. The plants are kept very warm and bright with a fan on them.

Any idea what's wrong and suggestions? Thanks!

SheilaJ