incuation advice needed

Any adivce would be appreciated,

we have 18 eggs in an automated incubator,
6 Welsummer eggs have been in for 18 days (put into incubator on 17.5.09 14.15)
6 Silver speckled sussex (put into incubator on 18.5.09 7.00am)
6 Rhode Island Red (put into incubator on 20.5.09 21.30

Did not have a lot of luck when we tried a manual Covatto 12  incubator for our first lot of eggs and lost themall, could have been anything, possibly some not firtile , not turning them right and found it hard to read the thermometer and was not to sure about the humidity. (no instruction book)

Because the eggs went into a new auto incubator  within 3 days of one another, is it possible to leave them all  in there?
OR
Transfer the 6 Welsummers to a Covatutto 12 co  manual incubator for the last 3 days for the humidity and not automatically turning

Thanks 

A separate thermometer and humidity gauge is a relatively cheap thing to get for the cuvatto.  You'll then know the humidity is high enough for hatching.