The plants described (apart from kamisensis which was not mentioned) are all native to the Roggeveld escarpment according to "The Color Encyclopedia of Cape Bulbs". Most likely the seeds find your conditions a bit too warm for germination since rainfall in their native range is restricted to the winter months when temperatures are quite cool with occasional frost.

Ideally you should seek a night temp of 4-7C and day temps of 14-19C. Since these temperatures are not comfortable for people, you might try to find an olr refrigerator and set the thermostat to the warmer setting. Have the seeds cooled at night and at room temperature with bright light during the day. The temperature oscilation is more critical to germination than the actual temperature. Do not let the temperature drop below 4C in the cooler or germination will come to a screeching halt!.

Just wanted to say that after leaving the seeds outside since early spring (April), all the remaining three species have finally germinated. Temperatures have been mostly around 5-10 degrees Celsius since September, but down to -3 degrees C some nights. None of the seedlings seem to have suffered from the low temperatures (or they may have germinated after the last cold period since the last month has been unusually warm for this time of the year.)