TMI - green baby poo

My baby is 20 days old and exclusive breastfed. The last few days his poo has been this colour rather than yellow. I thought it was something I ate but that would be long out of my system. I have been on iron tablets since he was born but assume that wouldnt change the colour this far into taking them. He does have difficulty latching on at times so I fear he is not getting the fatty milk. The breastfeeding specialists in my area arent that great and the few times they have been he has either been asleep, just fed or they havent been able to get him to latch right. Starting to worry. Any advice?