  Non-equilibrium dynamics of three dimensional model spin glasses - the Ising
system Fe$_{0.50}$Mn$_{0.50}$TiO$_3$ and the Heisenberg like system Ag(11 at%
Mn) - has been investigated by measurements of the isothermal time decay of the
low frequency ac-susceptibility after a quench from the paramagnetic to the
spin glass phase. It is found that the relaxation data measured at different
temperatures can be scaled according to predictions from the droplet scaling
model, provided that critical fluctuations are accounted for in the analyzes.
