Hi Christine,
Last week we deprecated our support for TLS 1.0 and 1.1, we provided this notice a number of times before it was deprecated last Mon, 07.16:
Agile Central TLS 1.0 and 1.1 Deprecation Notice
It sounds like your integration is something you developed yourself, so please double-check if you are using TLS 1.2 which is what we are supporting. Also, make certain the browsers are set to use TLS 1.2, see:
Enabling TLS 1.1 and TLS 1.2 on web browsers
The fact this is performing slowly is suggesting it's not the TLS issue (if the TLS issue then it should not work at all), but the timing is quite suspicious being right around our announcement.
Please look into all of this and let us know if you were aware of this deprecation, if your connector is/isn't using TLS 1.2 etc.. If after all this, still working and still slowly then you may need to create a support case.
Thanks,
Sagi