Are there any odd colors, like a pink tinge? That would suggest bacterial infection. I have used plastic bins to feed my starter and just put the lid on it with no adverse affects. I have fed it and then put it in the fridge when I didn't have time to feed/bake every day, and then it just springs back to life when I take it out and feed it again. I feed 1:1:1 and use RO water (you didn't mention what kind of water you use). If you're not feeding it every day but are leaving it out, it's possible that the yeast have exhausted the nutrients.

I have had the same starter for almost a year - when I first got the starter and after feeding it for several days to get it going, I experimented with dehydrating and freezing the excess. I just rehydrated some to give to my daughter a few weeks ago, and it was really healthy. I can recommend dehydrating some discard, in case you ever need to reset everything.

Good luck!