I seriously doubt if the driftwood contributed to the death of your fish,( depending on fish type and water parameters)if you had a disease in the tank it is still there. Regular water changes solves a lot of problems.
I removed some fry and found that the ones I did not move grew twice as Quick as the ones I did remove. ( if anyone would like some I still have about 40 going free, sized from 2cm to 5cm )
Ianab and SpidersWeb are bang on, your problem is the Daltons aquatic mix, it is so fine it hangs in the water for weeks. Patience and water changes are the answer.
I thoroughly enjoyed what I saw and think you guys have done an amazing job , some fabulous fish on show and the meal even more so, I take my hat off to all involved and give it 10 out of 10 as well as 5 stars. Thank you guys.