Hello! Plant newbie and 6a citrus killer here!

I seem to be inept at understanding my citrus’ needs. I have already killed a beloved key lime, only to become smitten with this lovely Meyer lemon tree, and I am afraid that she will follow in the key lime's footsteps towards death, due to my black thumb. They seem to be expressive trees, and yet it falls on deaf ears, as I don't speak/read citrus (where is Rosetta Stone when you need her!)

It's a Record Buck Farm Meyer Lemon that I repotted in a 12" clay pot, with wick, in a 511 mix (repti bark, peat, epsoma perlite, with osmocote plus and lime). I was not ballsy enough to bare root it, so there is still some nursery soil in roots. After a few days shade, I placed her on the south wall of the house and am trying to get the finger/ skewer method down to prevent the very common for me watering-to-death-method (TM). In the 80 high/60 low degree days I've watered every 3-4 days. I withheld fertilizer (other then osmocote in 511) waiting for new growth. Well, on the 13th day in her new pot she started turning yellow from the bottom up <insert "Beginners Citrus Panic" here>. I understood that yellowing of old leaves is due to nitrogen (?) So, I watered with 1/4 teas/gallon FP, no change. Not wanting to over water, I sprayed effected leaves with FP, no change. I sprinkled 2.5 teas Citrus Tone on soil, and lightly watered in, no change. It has been raining on and off for days so I am trying to be conservative with water, despite 511 mix.

So am I being too conservative with the fertilizer in this very draining mix? Too heavy-handed with the fertilizer? Too liberal with the water? Or, as usual...too panicky and likely to nurture-to-death? Advice wanted, or Xanax...