Indeed, these are excellent plates for a first try, and Irv’s advice is excellent and will help you find the best exposure. Those stains you have are unusual. Two thoughts. Is your plate too close to the iodine when you sensitize? And do you leave the plate in the hypo long enough to make sure you have removed all the unexposed silver halide?
Bien le bonjour à Mark, et je vous souhaite encore meilleure réussite pour vos prochaines plaques.
gregory