The exact N-P-K is not critical, and unless the soil is nutrient-deficient (only able to be determined by a laboratory soil test), the peonies probably don't need any supplemental nutrition at all, especially if they are growing well and have been mulched. (The mulch will compost over time and supply a few nutrients.) Plant-tone is listed by the manufacturer as having an N-P-K of 5-3-3. Rose-tone is listed as 4-3-2. While the peonies probably don't need either, either would probably be fine if you wanted to give the plants a mild dose based on package directions. If you wanted to choose one, rose-tone seems slightly more appropriate (proportionately more nitrogen by weight, though not by much), but it won't make a notable difference which you select. When plants are otherwise healthy, "less is more" is a good approach to have when considering the use of fertilizer, not only to avoid applying what isn't needed (and too much can stress roots), but also to avoid contaminating stormwater runoff with nutrients that pollute the Chesapeake watershed.

Miri