Semi-Hydro and Alkaline-Loving Plants

[Plantcrazed101]

Hi y'all,

This is slightly off topic, but I have a Cubanola domingensis that prefers alkaline soil. I've adjusted it to semi-hydro, and it has produced a beautiful set of roots! The only thing is, the plant is yellowing. Since I haven't been using anything other than my regular fertilizer and it hasn't really had much of a change in conditions (it's in slightly warmer, brighter conditions as I have moved it out of isolation..doesn't appear to be based on my research sensitive to light levels increasing a bit) my only guess is that the source of it's yellowing leaves has to do with it needing more alkalinity.

Since I'm sure I'll have orchids that need more alkaline water, how do you do that with semi-hydro? How much is too much?