How to best do contextual help in Web forms for Touch devices?

I've got a Web form that contains contextual help where necessary. There is a small 'help'-icon next to some fields and if an user hovers it with his cursor, a little tooltip fades in.

These tooltip can be problematic on mobile/touch devices. I've seen that some times they are cut off. Also tooltips don't have a good reputation in general for touch devices.

What do you recommend me to do? Should I think of something else than tooltips when it comes to touch devices? Can these tooltips be improved in some, so that they still can be used?

I'm thankful for your answers.