It may be possible that your crons are being piled up. If you have to run these crons at every one minute then you should better use sleep. What you can do is that just break your crons into 4 different crons and schedule then in following way
*/1 * * * * sleep 1; /cron/first
*/1 * * * * sleep 2; /cron/second
*/1 * * * * sleep 3; /cron/third
*/1 * * * * sleep 4; /cron/fourth
In this way your cron will not pile up and should run smoothly.
Best of Luck!