The solubility of sulphates in water down the Be group is $\mathrm{Be}>\mathrm{Mg}>\mathrm{Ca}>\mathrm{Sr}>\mathrm{Ba}$ This is due to

The hydration energy decreases from ${\mathrm{Be}}^{+2}$ to ${\mathrm{Ba}}^{+2}$ This causes the decrease in the solubilities of the sulphates in this order. In other words, the solubilities decreases with increase in the ionic size.