As mentioned by Murthy Sir, empty Hussainsagar (12702) rake got derailed while entering HYB on 27th, and started in the night. Due to RSA, 17031 from CSTM got delayed on 28th, arriving HYB about 7 hours late on 29th, and as a result, today's Hussainsagar from HYB is also delayed.
In a separate incident, VSKP-LTT had a loco failure in SC-WADI section (no problems in KYN-PUNE), resulting in delays for both 18519 and 12702 from that point. That's the reason for the late departure of 18520 from LTT today.