Paragraph text converted to artistic doesnt keep formatting, why?

like in the title, i start with a paragraph text frame to layout my text, i use full justify with all of it, but some of the lines that dont occupy the whole width of the frame and end with a paragraph mark( inverted p sign) and not all of them(even stranger, no?) are expanded to the whole width of the frame by adding a lot of annoying large spaces between characters when converting the frame to artistic. why is that, can this be disabled?

 

thank you, and please excuse the many repetitions!