Keeping bath toys mould free??

Just • 2 girls & baby girl no3 on her way 😘
My 3 year olds bath toys are forever going mouldy. Every time she has used them they get a good wash down with the shower head and then I put them in her bath toy holding rack thing but still they always end up getting black mould on them so I'm forever having to either throw out and replace them or bleach them and being pregnant again don't really wanna use bleach. 
Any tips??