Using Orchid Fertilizer (15-35-10) on my plant?

During first/second week of flowering (just starting to show the white pistils/hairs)?

I've had a totally organic grow so far, so I'm a bit reluctant to add a chemical fertilizer of any kind, nonetheless one designed for orchids...but all plants need the same macronutrients, so this ought to work, correct?

(plant is in pretty poor shape, by the way)

It is the correct ratio so you could use it. If the plants are already bad there is no harm in trying it. Don't overdo it though, gradually apply them

When flowering you need a low number of nit. mid number of phos. and a higher number of pot. is that correct?

yes hazemaster your right.. u need little nitrogen, and more phosphurous and potash....although nitrogen is still required.

Dont get caught up by the NPK ratio numbers thinking its an exact science,instead learn to give the plants what they need when they need it,a common mistake is to rely on the numbers instead of learning plant symptoms & how to correct them using the proper NPK ratio ferts.

Yes your ferts will work but pay attention to the plants & watch the low nitrogen level of your fert,depending on their growth spurt they may need a higher dose of nitrogen for a few feedings after the spurt has leveled off,also watch the phosphorus level which is easily over done by many.