congrats on the 21k .. PB I guess?
the 2k session is a very tough session mentally and it is the session that will develop you the most
in the 2k session you mention the heat, this has a major 'negative' impact on performance
never focus on the poor runs, focus on the ones that give you confidence
in the next 2k session, start slower and finish stronger, looking to do all 5, even if you run far slower in the first 2 build up and gain confidence
you don't lose pace as quickly as you think
how come you going to the 1k session?
over to you