I bought two budgies (2 months old) on Aug 7,2020 one blue and the other yellow. The blue one loved yellow one so much he always tried to preen her. But the yellow one kept hitting him and scaring him away. On 25 sep the blue one died after eating a new pet food ?? i think it had pesticides. 

The yellow one remained single for 2.5 months because my parents were not willing to get a new one as they were really upset. On 5th dec finally they agreed and we got one male 7 month old budgie(light blue). This time yellow budgie fell in love with him she tried to preen him. But he keeps hitting her?

 

Sorry for your loss. Female budgies are very picky about their mates for some reason. My first pair of budgies had pretty much the same thing going on until we got two more. The new boy Guapo immediately got the girl whilst poor Blue has been single for at least a year. I wouldn't be concerned about him hitting her as males aren't really aggressive. If she looks injured then it might be a problem (males can get quite excited). Just make sure to keep an eye on them in the mean time.

[not an expert By The Way]