Touring - Feet pain with climbing

On yesterdays climb, the last 15 miles or so the bottom of my feet really started hurting. Do not think it is hot foot but it was almost the entire area of the bottom of the feet. Why does this happen? Does it mean I should get stiffer sole shoes?

Are you wearing cleats or regular shoes on your rides? Your current soles could indeed be too flexy, possibly after years of use if they are they are the softer cycling/walk-around cleats. If it were heat or discomfort concentrated toward the front or "ball" of the foot, I would suggest to readjust your cleats. If the pain is on the entire foot, your shoes could be too narrow or tight. For a while years ago Shimano shoes were giving me lots of weird problems. I switched to a brand that made "wider" shoes (Pearl Izumi), problems solved.

Your feet need to be well supported by stiff soles and well fitting shoes. What do you have now?

Your feet may also be swelling. Simply loosening the straps or laces can help significantly.

Did You upgrade the insoles in the shoes above what is in them out of the box?..

Did You upgrade the insoles in the shoes above what is in them out of the box?..

no. should I have?

That is my approach.. My longest distance touring shoes are a loose fit,
shoe On toe clip pedals.. but I have my favorite insole in them ..
In my case they are cork composite Birkenstock, a 3/4 length.

casual pace,I ride all day, not significant discomfort.