Jolida Tube amp lost output one channel

So I seem to have lost output on the left channel of my Jolida 102B amp. Is it safe to assume it's the tubes and I should just replace them? All of them? I just picked this up a couple weeks ago so would hate to throw money at a lemon. I did have the speakers hooked up ass backwards, meaning they are 4-8ohm speakers and I unwittingly had one on 4 and one on 8 so maybe I damaged something more than the tubes? But, it has been working fine until I powered it up today and after the lack of sound I noted the mis wiring (it's only been that way about a week as I was trying out different speakers). Yeah, I've got a ways to go, please help?