multiple decay? (in General)

If you have multiple decays, would the first one half the HP, then the second one half it again, and so on?

Or can you not have multiple decay affect same minion?

Couldn't find anything in wiki about it

Example: minion X has 20k HP.

I have 3 decay minions for some reason, a b c
Would it work like:
Mmion A decay hits x for 10k
minion B decay hits x for 5k
Minion C decay hits x for 2.5k

So after first round of melee because of decay he is now at 2.5k HP.

It works as you stated.

you would need to watch out for amf if you are only going base decay

Yes but to effectively use it(as said above me) decay's damage actually decays once AMF is cast against whichever minion(s) is using the DD skill. To counter it you have to train more into Decay to counter the effects of AMF.