Contrasting magnetic behavior in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>MnSc</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>X</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math>

The spinel compounds ${\mathrm{MnSc}}_{2}{X}_{4}$ are highly frustrated and candidate materials for vortex-like 3 q magnetic states, such as skyrmions, with propagation vectors in the [111] plane. Because of the strong magnetoelastic coupling, we could extract a refined magnetic $(H,T)$ phase diagram for ${\mathrm{MnSc}}_{2}{\mathrm{S}}_{4}$ from ultrasound and dilatometry measurements. We found a variety of magnetic phases, including the skyrmion phase, which is stable down to lowest temperatures. In comparison, we investigated ${\mathrm{MnSc}}_{2}{\mathrm{Se}}_{4}$, having a larger distance between the magnetic ${\mathrm{Mn}}^{3+}$ ions using the same methods. Unlike in ${\mathrm{MnSc}}_{2}{\mathrm{S}}_{4}$, we found no skyrmion phase and overall a lack of sharp anomalies indicative of phase transitions, neither in dilatometry nor ultrasound nor in specific heat and ac-susceptibility data. Motivated by our findings, we performed model calculations, which reproduced the experimentally observed magnetostriction and specific-heat results reasonably well.