Recipe Testing Questions

Hi all, am looking for a little advice on some recent naturally leavened loaves I baked. I'm trying to get away from using so much commercial yeast, so I decided to make my standard country sourdough, and tot totally experiment with a rye and whole wheat sourdough. I use a locally milled hard red wheat flour, #60 grind for the starter and the country, #18 grind for the rye. The rye flour was also a #60 grind.

I keep my starter at about 90% hydration, feeding it:
50g active starter
250g #60 grind HRW flour
225g H2O

The country sourdough formula was:
Autolyse, 30 minutes:
HRW #60 - 425g
H2O - 350g

For the final dough:
Active starter - 100g
Salt - 10g

For the rye, it was:
#60 Rye flour - 300g
#18 HRW flour - 150g
Active starter - 100g
Salt - 8g
H2O - 350g

The schedule was the same for both:
Mix starter at 8pm Wednesday evening
Autolyse country 10am Thursday
Mix final dough 10:30am Thursday
Give country three folds, 20 minutes apart
Bulk ferment until 9pm
Shape and put in fridge 9pm Thursay
Proof overnight
Bake 9am Friday, 30 minutes at 450 in dutch oven with lid on, 20 minutes lid off.

The issue is that they both came out rather flat. This was the country:

And this was the rye:

Both loaves had a pretty nice, even crumb, although obviously not terribly open, and both have really nice flavor, so I don't think the issue is so much a formula one, but maybe a timing or technique one? I did not use any mechanical mixing. My oven is pretty awful (to keep it at 450 I have to keep it set to 500), so that may account for some of the lack of spring, but even considering that, I've gotten some really nice loaves and whenever I bake loaves with commercial yeast, they do rise, so it's not the only issue.

The rye was a total experiment, I just kinda tossed some numbers out based on a rye sandwich loaf recipe that I have, so there is that too.

Any thoughts on what I could do better next time to get more spring out of them? Any glaring flaws in the formulas I should address? 

Thanks!