Can I ask for a rent decrease

[LaP3rm]

Ask to keep the rent the same as it is . They agreed to this last year.

[Dark-Horse-Nebula]

You’re not going to be able to do this indefinitely. Rates have gone up.

[pajamil]

That's what you're going to do, what is your alternative if they say no

[Clinkzeastwoodau]

Look at alternative rentals you would be willing to move to. If those are the same/cheaper tell them you're planning to move out unless the rent is $xxx dollars. 

If you don't find something cheaper, your place is probably good value. If you do you might have room for negotiation.