are you having trouble with you own developer and their emulsion.
from others i have spoken with who home-brewed their own developer using
thiocyanate and thisulphate always had trouble ... but when they just used
the developer supplied by rockland they had no trouble at all.

when the weather gets cooler i'll be making rockland dry tintypes again
i did it a little in the spring and it was fun ...
i would love to do dry collodion plates, but i keep having dreams where things
go b-o-o-m ( i used to use collodion in the 80s + 90s ) ...

good luck