lower leg issues

So, I've worked my way up from walking 10 mins once a day to about 4 km twice a day (8km total, roughly) over 6 weeks. But now, my calves are really not liking hills/inclines/gradients - but ONLY if I wear my sneakers. On the flat there are no issues. I can wear these same shoes all day without any other problems. They are new by the way. But not so new that this is an 'adjustment' issue. Two weeks ago I didn't have half as much discomfort.

If I wear my beat up old sneakers or the slip on's (not sports wear - but also new 2 months or so ago), I get wicked front leg pain on my right side (tibialis anterior if I have my anatomy right), but no calf discomfort.

The calf thing is tightness, not soreness and both issues resolve after a 2 min rest + calf stretching.

I plan to see if I can visit the local podiatrist in case there is an actual foot fall thing happening. No clue if I am old enough to see him though, (he has lots of pamphlets geared to older people).

I don't want to stop walking obviously, but I am at a loss as to how to fix/deal with either issue. I am trying to stay hydrated, and I do stretch (perhaps not enough? or accurately?) Am I over doing things? Should my legs have adjusted to the route I take by now?

If this is in the wrong place or I shouldn't be asking, please let me know