Maggots in rabbit food

I’m embarrassed that it didn’t occurred to me that it could potentially be a problem at the time. So Before I got my rabbits, I went online and purchased a 10kg pack of Burgess excel rabbit nuggets for dwarf rabbit, I kept it in an airtight container (simplehuman pet food bin). And probably a week later, when I opened it to get their nuggets, I saw 2 maggots on the inside of the lid of the container, at the time I just throw the maggots away and continue feeding my rabbits as normal. Now that I’m thinking about switching their food to adult food, I’m wondering if I should’ve discarded the whole 10kg of nuggets when I found the maggots (I’ve been reading about flystrikes).
I’m based in the UK, I’ve never seen a maggot even in the hottest summer time and I only got the pack in September 19, so it must’ve come with the pack.
Should I have discarded the food? Should I continue feeding them this food? Does this make me a bad bunny mum?

Side question: do I need to change their food to adult food when they reach 6 months if they are dwarf rabbits? (4 and 5 months indoor rabbits)

I can't say anything about the maggot situation except that the batch was bad and it may not be safe, but you should slowly start tthe transition from young to adult rabbit food. Most rabbits are considered young adults around 4-6 months depending on gender.

It could be moth larva, which would be more likely. Fly maggots need moisture, which shouldn't be in pellets(or they mold, which is toxic to rabbits). Moth larva isn't completely unusual in hay and hay products. It's up to you if you want to get rid of it, but I don't know of any reason it would be harmful for rabbits.

I find moth larvae in most bird seed I buy for my birds. I freeze the bag of seed for 24 hours which kills the larvae and prevents me from ending up with a bunch of tiny moths!