I've been having consistent problems with my loaves deflating during scoring and little to no oven spring. From what I've been reading, this usually indicates over-proofed dough, but I really don't let the dough proof very long (30 minutes - 1 hour) and when I poke it before scoring, the dough still slowly rebounds.

I'm wondering if this could be an indication of dough strength instead of over-proofed dough. I really don't know what "strength" means, but I've read it could be a problem when scoring.

My breads are whole-grain (ground myself) typically either Hard White Spring or a mixture with Hard Red Spring. I'm using the Reinhart whole wheat method (biga, soaker, fridge for a day, etc...). Also using the stretch-and-fold (~4-6 folds w/half hour rests) instead of kneading.

So, any ideas on if this is a strengh issue or over-proofing? If it's strength, any tips on increasing the strength of the dough?