t5 ballast questions

i bought a t5 2' 4 bulb light fixture from my local hydroshop. that was 4 months ago and since then the shop got sold to new owners. same store just new owners. would they warrenty my ligt as it should come with a 1 yr no hassle warranty.
my problem is 1 light outta the 4 works fine the other 3 work but are really dull. switxhed the bulb and its still the same. really really dull. thinking its my ballast.
has any one switched a ballast on these?

I was looking at ballast on the inter webzzz after I figured out it was the wasn't the sockets and they wanted 50 bones plus shipping Went to the bulb man in my city had a ballast in stock for 35 bones.
No schematic so wiring up the bitch was hard. Took me 5 min to put in and about 1 hr switching wires around from socket to socket til I got all my lights working. Really easy now I've done it once.
Glad I saved my 110 dollar light for 35 bones.
Thanks again for at least replying I figured the new company would tell me that. So I didn't bother.