I'm no potting-mix expert but here are some thoughts.
1- Some low-quality coconut coir contains large amounts of salt. Salt can quickly kill plants so that is a possibility.
2- In the second mix, you added "burnt wood." Wood ash is very alkaline and can burn plants' roots.
There are also some other issues that would cause long-term problems but wouldn't have killed your plants in two day's time.
1- Your first mix sounds like it would hold way too much water.
2- In the second mix you added "red mulch." Red-dyed mulch is made from the actual wood of trees and not the bark. Wood should not be used in a potting mix because the microorganisms that decompose the wood will use up the nitrogen in the mix and leave none for the plant. It is made to put on top of the soil but not incorporated into it. Also, red-dyed mulch is usually made from recycled wood which can, sometimes, come from questionable sources that may contain some nasty chemicals.
Since you are very new at gardening, I think you would have better luck purchasing a good quality, commercial soil-less potting mix for most plants (if it is available to you, of course.) When you've learned more about your plants and their needs then you can start experimenting with making your own mix.
In the USA, a good, store-bought potting mix usually contains peat moss, vermiculite, perlite and, sometimes, conifer bark (also a bit of lime to balance the pH and some fertilizer.) However, I'm not sure what is used in Malaysia since ingredients tend to vary by region and availability.
If you are starting with seedlings, like the kai lan sprouts, then you'd probably want to keep the mix fairly simple. An excess of fertilizer can actually harm plants, especially tender seedlings. It is a balancing act.
to ATP!
