Can't seem to check the tier of an active potion effect

[DevDav]

Hi,

on my SMP server, whenever you respawn you gain resistance at level 255 for 10 minutes as a sort of "grace period". Now I have this working jolly good and exactly how I want it to, but I also realized that someone could abuse this grace period by unfairly PVPing someone while they are invulnerable. So to remedy this, I need a way to disable fighting other players for any player who is in the grace period. I thought I could do this by checking if a player has resistance at tier 255, and while I can check if a player has resistance, I can't seem to figure out how to check what tier the effect is on! So I ended up making this Skript:

on damage of a player:
	if attacker is a player:
		loop active potion effects of attacker:
			if type of loop-potion effect is resistance:
				cancel event

And it works, the only problem is, without a way to check the tier of the resistance effect this also disables PVPing for players with resistance through a beacon or turtle master potion or any other legit method, which is unideal. Could anyone help me with this problem? How do you check the tier of a player's active potion effect?

Thanks in advance.