We want everyone to be able to receive your messages, itsjustmejanie91. If this is only happening with iPhone recipients, then the issue may be caused by a common issue with iPhones.
This is that it is very common for them to not be able to receive a MMS(picture message) while connected to Wi-Fi. Have you asked them to test this out while not connected to Wi-Fi? Also, have you tested your phone using the native messaging app the phone came with instead of our Message+ app?