It's a 15-9-12 formula. That's a very good formulation for daylilies, but people should be aware that in certain soils, phosphorus can collect, or "bind", and there is a real possibility of inducing phosphorus toxicity through over-application or years of accumulation.
Because most good garden soils contain adequate amounts of phosphorus and potash, many daylily growers are using fertilizer formulations which are higher in nitrogen.
There's a very good link on Rich Howard's CT Daylily site;
A soil test is always advised in order to establish a baseline for future feeding.
As a side note, periods of high temperatures and humidity along with plentiful rainfall have been known to cause some time-release fertilizers to "dump". That's worth looking into as well. I don't really get that type of weather, but because I grow in containers (which often run warmer than the earth), and water lightly but more often, I apply time-release fertilizers at reduced rates, as a "nutrition insurance" baseline, and supplement with liquid fertilizers whenever I feel the plants need a little boost. For that I use half-strength Dyna-Gro Foliage Pro (9-3-6) to which I add nitrogen using General Hydroponics FloraMicro (5-0-1).