Mixing tretinoin and adapalene for anti-aging, good or bad idea? (Photo)

I use tretinoin 0.1% every night but I find that using a peasize for the whole face + neck on dry skin is not enough, the recommended dosage simply will not cover the whole area. Yesterday I mixed my tretinoin with half a peasize of differin gel 0.1% and this made the spreading much easier. Is this OK to do or am I diluting/buffering the tretinoin and missing out on optimal results? I use the tretinoin mostly for anti-aging purposes. Kind regards.