I just picked up some new rhodo (/azalea/camellia) food, and noticed when I brought it home that the ratio is completely different than my old box: 10-6-8 vs 4-12-8. Hard for me to believe such different formulas are both specific to rhodos! I had naively assumed rhodo food was rhodo food. Has the recommended ratio changed since I last bought fertilizer, or are there different formulas to suit different soil conditions or what? Thanks!
The first one has a higher nitrogen, so you would promote foliage growth. The second one would be better suited to promoting flower health and growth. The soil should be acidic. I would scratch some peat moss into the soil and spray the leaves with Iron chelate.
Whenever you buy a fertilizer, without soil testing beforehand being involved it is a crap shoot. It may or may not have the right ratio for the soil it is being put on. Likewise recommendations such as the foregoing may or may not be of use to your particular situation, without seeing a soil test report a body is not in a position to make valid prescriptions - beyond those thought to be applicable generally throughout a geographic area. An example is the fact that rhododendrons are not likely to appreciate scratching of the soil among their tightly dispersed and delicate roots. And the fact that mulches such as peat are of use by making a blanket of different material over the top of the soil, mixing the mulch layer with the soil beneath reduces this effect.