What's eating my Hot Lips

[MaggieMcGill]

Hi, hoping someone can help with this, fairly novice gardener here. I bought 3 hot lips plug plants early spring. They have been doing great and have grown lots but something seems to be eating the leaves. They are just disappearing and it's like a clean cut at the steam. One plant's remaining leaves have also started going a funny brown/red colour and it doesn't look healthy. They are all in pots.

I'd suspect leaf drop due to drought, actually, rather than eating. Are the leaves on the ground or have they disappeared entirely?

No leaves on the ground, I have found the flowers on the ground but not the leaves. This one is at the back of the house, it is the healthiest looking but it's still missing leaves.