Custom Form Not User Friendly on iphone/Safari

Site URL: http://mombitious.ca

Hello. Im wondering if anyone has any idea why a certain portion of my website ordering process gets glitchy. I just opened mombitious.ca.

When looking on an iPhone, the final "Custom Form" that I have set up gets cut off and becomes impossible to complete. I have a Custom Form asking the customer to include a custom message for a card. When they begin typing their custom message, the screen layout flips and cuts off the input text fields and "Add to Cart"  button at the bottom of the page.

This only appears to be a problem with iPhones running Safari. Android devices using a mobile Chrome browser seem fine.

If anyone can please try and let me know, I would love the help!

Thanks in advance,

Mombitious Canada