These are indeed Krzyz Zaslugi (Cross of Merit) in gold, silver and bronze. Due to the monogram PRL, they were produced after 1952 when "RP" changed to "PRL". In Communist Poland (roughly 1944-1989) the "sword-attachment" was abolished for the military branch of Krzyz Zaslugi and hence it's impossible to say, if your 3 crosses were awarded to civilians or military personel. In Communist Poland you wouldn't receive Krzyz Zaslugi for bravery in combat, but rather for long, flawless service.
The bronze cross seems like a late 1970s / early 1980s issue: worth 6-8 usd.
The silver cross seems like a 1960s / early 1970s issue. If there is some kind of stamp on the reverse, then it's before 1965 (roughly) and price will be a bit higher: worth (w/o stamp) around 10 usd.
The gold cross has a clear stamp on the reverse, which is not the maker (all 3 crosses were produced by the National Mint), but rather an "approval stamp" showing that this exact cross fulfilled the standards. I think I have some 30 different combinations of letters and numbers defining who approved the medal. Due to the approval stamp this cross is probably worth around 20-25 usd.
Regards Aahauge