I think I would be leaning toward the hoses and bucket being the issue. I've never used buckets, so I don't know how often they go bad. As far as hoses, I have been using the same hoses for a couple years now but will probably replace them before too long. The previous one I had for 3 years and never had a problem with it.
For you starters, are you boiling up some DME/LME and putting it in the clean/sanitized glass jug with a funnel? I did exactly that for a long time before I got my stir plate stuff, so now I boil right in the Erlenmeyer flask. Also, do you taste your starters before you use them? I generally get a little bit out and try it before I pour it in the beer just to make sure it is happy (usually just some of the spent wort that I'm decanting anyway).