It's not feminine. In plural there are only two genders: masculine personal plural and everything else. This means you can use 'małe' with nouns such as 'psy' (dogs - masculine, but not personal), 'kobiety' (women - feminine), 'dzieci' (children - neuter) etc.

On the other hand you would say 'mali chłopcy' (little boys, masculine personal), 'mali mężczyźni' (little men), 'mali ludzie' (little people), etc.

"Jabłka" is plural Accusative form of "jabłko". And the noun remains neuter.