Historical is not shown, except for only last 15 days (Grafana)

Hi All,
Im running Grafana 6.4.3 + Prometheus 2.3.2 for more than 9 months, but few days ago I noticed that Historical metrics are not being shown, only last 15 days.
Dont know what happened, as it was working fine, I havent applied any changes as upgrades or patching on instance.
In below screenshot will see, is showing only from July 1st and for the “last 30 days”, hope someha has walked through on this kind of issue and can provide any support, will really appreciate it.

Thanks & regards