New phal spike so soon after blooms dropped?

[bday_phal]

I bought this Phal from a garden center of local home improvement store. I had eyed it previously, then it was marked down to half price so it had to come home with me.

The garden center lady told me the blooms had another 2 weeks or so.... They did. This being my first seemingly healthy Phal- I am very invested in her activity (first one ever- a birthday gift- was watered beyond wet before I ever got it, and though still green is slowly dying from no viable roots , imo.)

Back to this girl- so I read that new root growth often occurs after flower drop. I cut the spike back between lower nodes and saw what I thought was root growth. Then realized it is a new spike already ! as well as some new root growth. (both pictured)

Question-- is this usual? for a new spike to spring up so soon? I assumed a period of 'rest' and re-spiking down the road, so I wanted to have your thoughts on this.

I'm not thrilled as the medium is not bark but sphagnum?
and I can only assume the health of this plant (please lawd !) from what little I can peek at from the surface.

If this spike proves sound and continues into bloom- which fertilizer is better. I have "regular" 20-14-13 and a "bloom boost" 11-35-15. These are the only two that were available. They are AOS endorsed and basically says use the bloom boost every 4th watering.

So is that once blooms show up, all year round, only when in spike/flourescence? (sp) or just every single 4th time?

thanks so much for your time and reply.