Spreading the emulsion on the plates is a bit of a trick.
Typical faults are
1) the emulsion not sticking in places - it pulls back as it dries - leaving the backing showing, hence black areas
2) the emulsion is too thick. This crazes as it dries - typically into wavy lines with a matt finish.
You seem to have both!
Rockland plates are pretty good at adhesion, certainly far better than the plates I use, which are alloy sheet sprayed with black cellulose paint (auto touch up).
Possible solutions:
Wipe plates with iso-propyl alcohol before use
add a couple of drops of wetting agent to the emulsion before spreading
The emulsion will only spread thinly enough if sufficiently warm to flow easily across the plate.
It really does need to be pretty thinly spread - most people who are starting out make it too thick.
This is just 'practice makes perfect'.
Good luck!
Simon