They will essentially stop producing leaves. It may be a little bitter. I would pull them plants and replant some seeds.

It usually does turn bitter. Try a leaf and see. If it has been grown under cool, moist and shady conditions, it is less likely to be bitter.
I'm not sure when you planted it but spring spinach should be planted as early as humanly possible - when the snow has melted off and the soil has dried out enough to work. You can sow spinach again in mid-August for a fall crop.

We are having extreme tempatures still and I am unsure when to plant in the fall. Normally I would do it in mid august but is there a rule of thumb temp. wise? I know toms don't pollinate if it is cooler then 70 at night, or so I have heard what about spinach is there a rule? I hate to waste seed but I still have toms and would love some salads! Any advice would be appreciated. I live in NW Ark.

Spinach is not something you worry about pollination. The problem becomes germination of the seed. They are planted very shallow and the trick is to keep them damp and avoid high soil temps. Shade and water are essential here in Georgia for a fall planting.