Oh...tuning a fret down. That is problematic. Because under the tape, most "regular" gauge tapewounds (@ 60-135) are actually more like a set of 45's in tension, which may be slightly loose for a down tune, depending on how your technique is. The nylon wrap does not add to the tension of the strings. I have played at times all the domestic tapewound strings over the decades, starting with the original Fender nylon sleeve strings from the 70's, current Fenders, everything in the La Bella stock line, D'Addario, GHS, Rotosound, etc.
To keep tone, consistency and at least some degree of stability tuning a fret down, the best strings are the La Bella Tapes in regular gauge, 60-135. The blacks are a little darker in tone, and the whites are a little brighter in tone, in the context of nylon wrap strings. You will have to have your nut either modified or get a new nut to accommodate the strings. Search the nylon tape threads, and you will find my posts on comparing everything and my measuring of dead strings after taking the nylon tape off to get the equivalent round wound gauges.