when one sand soldier is played, do all of my other sand soldiers get weapon master too with azir emperor of the sands?

No — only the Sand Soldier you're actually playing triggers Weaponmaster. It's a Play Effect ("When you play me…"), so the trigger is tied to that permanent entering the board, not to other Sand Soldiers already in play (Rule 821.1.c).

Two things reinforce this: Weaponmaster "has no function while on the board" (Rule 821.2), so a Sand Soldier sitting at a battlefield with the keyword does nothing until it's played again — which tokens never are — and each instance of Weaponmaster that triggers chooses its own Equipment, so you'd only ever get one Equip per Sand Soldier played.

Note the two Emperor of the Sands printings differ slightly ("Your Sand Soldiers have [Weaponmaster]" vs. "Sand Soldiers you play have [Weaponmaster]"), but the outcome is the same either way — the keyword is granted as the token is played, and it only fires for that token.