Thats the difficulty with fish and pets in general. It's all relative to your set up. I need to keep my ph low for my apistogrammas, cardinals, rummy nose and gold nugget so I have co2 and bogwood and very rarely do any water changes only really top up through condensation. So if I tell you to do it like this because it works for me that will be bad for your own fish. I would take a lot of advise (just in general) with a pinch of salt so this kind of thing doesn't happen again.

Regarding the bloodworm, doubt it's gamma rayed so try and get marine frozen as this is mostly always gamma'd. Doubt it's the cause but depends how long it was thawed during getting to the shop.

Could be may other things that only discus would be stressing over. I think the lack of trace elements and minerals from ro water is to blame personally but could be too much light. Some other fish stressing them, not enough hiding places, too much flow, also can't see your ph anywhere may be too low as many discus are being bred in ph around 7. Just a few out of a possible 100 what it could be

We got the blood worm from Pets At Home and we used it twice as the fish really didnt seem to enjoy it. The smell wasnt pleasant even when frozen.

I have gone back to tap water with tap safe in it. Am feeding them the bloodworm we used to which they are digging into.

Thank you for your response. We do have live plants and 2 pieces of bog wood. The Discus hide behind the plants but will add more places as soon as i find what i am looking for. So will do that search now and buy it today.

I plan to do whatever it takes to prevent another fish dying in my tank. I know it will happen but still upsets me.