That's vinegar syndrome and it cannot be halted or reversed. The base has entered an auto-catalytic state, whereby the base feeds upon itself and it will only end in disintegration of the entire negative.
It's not "bad film", but the specific batch of "dope" used to form the base might have been more acidic than other batches OR the particular emulsion might have used a subbing layer that is more prone to kicking-off VS, but I can only speculate.
I highly doubt the emulsion can be floated off the base, but it can be worth a try after you make the best copies possible in their current condition.
Segregate these affected negatives from other "healthy" negatives, as the byproducts of the reaction can "infect" other negatives. Iron is an accelerator; keep them away from any iron enclosures.
Molecular sieves can be used in their air-tight container to scavenge the acid vapors that are a byproduct of the decomposition, but it will only slow down the progression and it can't be halted or reversed.