Wow, nice and short internodes.
Honestly, I have not worked out a bonsai blueberry fertilizer program, yet. I only know what we did on the farm.
Blueberries can not absorb or use nitrates in any way. Blueberry fertilizer MUST supply nitrogen as ammonia, or ammonium ion, or as amino acids. Inorganic fertilizer would be ammonium sulfate based to encourage soil acidity, organic fertilizer like fish emulsion would supply amino acids.
Keep it dilute or none in spring thru fruit ripening, then moderation after fruit harvest thru to beginning of autumn. Then none at all over winter.