Diarrhoea

[Leenknegt-Lioen]

Hi!

Daedalus (male, about five months) has diarrhoea, I noticed it yesterday.
His cagemate Icaros doesn't have it. They both look very healthy, lively,
curious as ever. I gave them a strawberry a few days ago (my dad said I
shouldn't have done that), could this be it?
Today, it seems a bit more compact (the feces), but I wanted to ask: is
there anything I can do to help him?

Thanks for any help, I'm probably just being overworried, but I know
diarrhoea can be very serious.
Sarah