I have found that I get a sweet pickle smell when I ferment our food. It grows stronger each day that passes but turns more of a sour smell after day 3.5. I always find the empty container smells "gross" after I empty it to feed that day. I can't really describe the smell, but a friend who enjoys fermenting all of their own food to eat ensured me it's a completely normal smell (she's been fermenting things for years and hasn't had issues so I feel like she's on to something lol)
I ferment their feed for 3 days. I have a really simple system - 4 plastic tubs (the ones that organic greens come in from the grocery store) with lids that I rotate on an previously unused microwave cart with shelves. Day 1's container when I first started = their measured out food, a splash of apple cider vinegar then water to cover, plus about an inch. That container got moved into Day 2's slot, started another Day 1 and did that until there was a container in Day 3/had been fermenting for 3 days. On that day, I took the food out to feed them and poured some the water into the 4th plastic tub to start a Day 1. Waaah la. It takes about 3 mins in the morning to rotate the bins into their new spots, empty that days feed into trays to take outside and start a new bin.
I like doing it this way in smaller batches for a few reasons
1) I can control how much food they are given daily without taking a ton of time to measure or scoop
2) if a batch goes sour/grows mold, I haven't lost a ton of feed or a big interruption in the process
3) the rotation/moving of the bins gives it the jostle/stirring it needs to keep fermenting
4) anyone else can feed them the appropriate amount of food and start a new one easily with the handle measuring cup I keep next to the feed bin.