18month and 3.5 year old both waking 5am

I have tried everything Later bedtime , earlier bedtime . Grow clock , calcium gummies, more active day, black out blinds , they are both warm enough . And they both wake up at 5am and won’t go back down and I don’t know what to do I am so tired it’s been going on for 2 months now . I’m happy to wake up at 6am but it’s just so hard as I also work and they are both exhausted and moany by 4pm. They both used to sleep until 7-7.30 and it’s just changed over night .