How big is the pot and have you kept everything watered. Seems like a lot of plants for one pot to me.

No, it won't be the nasturtiums, it'll be not enough root room. Honeysuckle needs a large pot to itself, as does clematis.

Thank you for your responses. Once the nasturtiums are over I will take them out & not put anything else in with the clematis or the honeysuckle

Regards

I would suggest that you also un-pot both the clematis and honeysuckle later in the year and repot in separate containers. They are not going to be happy together in the long run.