OK everything is fine now that I removed the mixed wild bird seeds that were purchased from B&Q.
They're accepting oats and dandelion seeds now and 1 Dubia Roach was appreciated by the whole colony last night.
The crazy workers that were isolated returned back to the colony and have regained sanity.
Only one ant died but I'm very relieved.
Messor Arenarius are very beautiful ants and I would recommend them to anyone.