You started at 5 am: early morning runs can be very very sluggish even for people who are good at running.
10 miles a week, while respectable, is simply not a lot. Just keep increasing, slowly, the weakly volume.
There’s an overemphasis lately on the easy runs. Sometimes you should get tired. Sometimes very tired. Maybe once every 2 weeks, since you’re only running 3x a week. Consider some fartleks.
Edit: some additions:
Almost against the previous point but not really: while you should get very tired sometimes, easy runs have to feel easy/comfortable. Forget what your watch is telling you about heart rates and zones and all that. Listen to your body.
5.Your legs getting tired could be a number of things: lactate build up (going too fast),not enough recovery from harder runs/leg strength workouts, muscle fatigue from being unconditioned to longer runs (solution is also to just keep running more and easy).
Have patiente. Don’t force a pace that is not there yet, let it come naturally as a consequence of sustainable long term training.
A few things:
Edit: some additions:
5.Your legs getting tired could be a number of things: lactate build up (going too fast),not enough recovery from harder runs/leg strength workouts, muscle fatigue from being unconditioned to longer runs (solution is also to just keep running more and easy).