In a ranch, Pufts do not breathe enough when hungry. In fact, they go into starvation when surrounded by perfectly fine polluted oxygen with more than enough pressure. They all also tend to sit all in the same tile, which is kind of stupid and may or may not be related to the problem. Also, the constant alerts about "critter starvation" are really annoying.
Incidentally, this seems to kill off my Puft population, as they stay at 100% reproduction, then get starving, hence no egg. After grooming, they become non-glum for far too short a time to lay that egg. I think I will eliminate Pufts from my current game, they seem to be fundamentally broken and are just not worth the hassle.
And another update: Loading the game, all eggs drop. You should probably get your run-time-system fixed sometime soon, it is starting to sabotage the game experience.
Build vertical ranch 6 tiles wide, put in Pufts, see effect.