The word ᴱQ. eule “lamb” appeared in the Qenya Lexicon of the 1910s as a derivative of the early root ᴱ√EWE (QL/36). Unglossed ᴱQ. eulitse seems to be a diminutive form = “✱little lamb”
Neo-Quenya: I would retain this word as ᴺQ. eulë for purposes of Neo-Quenya; Helge Fausganger used this word for “lamb” in his Neo-Quenya New Testament (NQNT).
The word G. iol “lamb” appeared in the Gnomish Lexicon of the 1910s (GL/51), clearly a cognate of ᴱQ. eule of the same meaning from the early root ᴱ√EWE (QL/36), since eu usually became io in Gnomish. G. iolinc “little lamb, lambkin” is a diminutive form (GL/51).
Neo-Sindarin: I would adapt this word as ᴺS. ŷl “lamb” for purposes of Neo-Sindarin, since eu usually became ȳ in Sindarin.