Second production cycle (after molting) with under predictable production

I faced on a flock that its production stopped about 65% production rate after molting (for about 3 weeks in this percentage). Birds breed are LSL, their first cycle performance was good (more than 90% till 52 weeks of age, FCR about 2.1 till 70 weeks, mortality rate is normal). Molting lasted about 2 months and it was done at 85 weeks of age (because of management decision). Now the flock seems normal in terms of health (we checked ND, AI H9N2 serology). No symptoms are seen. Conditional factors are well (the house capacity is 30,000 with 3 floors cages; full automated). Does anybody have such an experience? Any suggestion?