Does the blockchain balance show up higher or the wallet balance? A single private key uses multiple addresses for privacy purposes so that people won't track down your total coin holdings. Your wallet could have shown the total balances associated with all the addresses which might be higher than the blockchain balance of the particular single address.
At rare cases, you would have sent a transaction with nil fee which would have stayed there in mempool for longer days. Once it has reached the threshold it could have came back to the older address from where it was sent. This return back might not have been updated in the electrum wallet. These kinds of issues won't occur unless you have a older version of electrum or you haven't connected them to the network!
Or the other situation might be, you would have received the coins in the address, but it wouldn't have been confirmed by the network due to lower fees. During this time, the blockchain shows the address with balances higher but the wallet shows balances only after 1 confirmation.