There is no rush to trade Galvis or Rupp or Hernandez, if they're not good enough to be building blocks, then it's unlikely they'll garner a big return, and none of the players behind them have shown that they're ML ready.
Just by maintaining their current level of play they increase their value (by providing buyers with more confidence that it's their norm, not a fluke) while giving time for their replacements to mature.
So it would make more sense to trade them in July or next winter than now.
Fans in every sport seem not to get the basics of a rebuild, patience, the whole point is to build up talent, not panic and make moves just to make moves.
The value of players doesn't decline because you have surplus talent, there are probably 10-15 teams for whom these three would be an upgrade, and if Crawford, Alfaro force their way into the Phillies lineup, these three will still be upgrades for those potential trade partners. So there is little downside risk and substantial upside potential (example, if Galvis' second half surge is for real and he does it for 300 PA before Crawford is promoted, he'd be a hot July commodity).