Originally Posted by Steve Smith
But here's something else. You should try to print them, in order to decide for yourself. PRACTICE makes perfect – even, or especially, if imperfect to begin with.
Your stated (probably) insignificant increase of development temperature at recommended time and developer should have resulted in a denser negative. Your impression of their thinness may:
1) be incorrect – that's why you should print them yourself.
2) indicate incorrect timing, thermometer readings, expired chemicals – in short anything in the process not operating incorrectly.
3) be the result of underexposure of the film itself, either by you or the taking device or light meter.