Colour of Discus Eggs

[The Lumpfish Guy]

If they are exposed to a stress factor like poor water quality then yes they might continue to breed, but sick discus don't breed. That is to say if the fish has a disease that is adversely affecting its health (not including TB), it won't come into breeding condition. The fish were producing eggs quite regularly, which would suggest they weren't sick.

That's irrelevant, we are talking about fish which are already committed to breeding, which had the disease in between breeding cycles.

they fell sick after we transferred them into the community tank to wean off the fry from mum and have more space to grow

So if these fish were ill and even if not, it is possible that they already had begun the commitment to vitilogenisis before"illness" and the treatment would have had an effect on egg quality too.

When the eggs have made the commitment to vitelogenisis, they will continue to mature and on to spawning even if there is a disease present. They will do this at the expense of somatic tissue, egg quality and in extreme cases this does cause egg atresia and re-absorbtion however it doesn't sound like it was a major stress ( might not have even been ill).

If you can get access to it this paper is a very good review on the effect of stress on egg quality
https://www.sciencedirect.com/science/article/pii/B9780444509130500059