It could be that your phone as a limitation that it does not support more Bluetooth devices.
Note that this community provides support for the Hue Essentials app. We do not offer support for the official Philips Hue app, so please get in touch with Philips Hue about their app.
You could try connecting the lights to our Hue Essentials app and see if that works.
Alternatively, a Hue bridge will solve this situation and the connection will be more stable as well.