Great advice from @Mimi-Simon , and I think she figured out the best placement based on those panels. However, those panels aren't optimally planned with text in mind from the start. With the placement of the art, you kind of have no choice but to push the speech bubbles to the corner to make space. The first 4 panels have the text at the top above the art - which isn't ideal because the reader's eye tend to jump from text to text and if you create a straight line above the art between the bubbles, the reader will end up completely jumping over the art and not looking at it. Basically, I recommend spending more time at the thumbnail stage to plan sufficient space for both your art and speech bubbles! The bubbles are an integral part of the visual and need to be taken into account when planning your layout and composition.
Lastly, while I think your speech bubbles aren't too big, I think the text within could be just a smidge smaller so you have a bit more of a margin between the text and the edge of the bubble. Right now, the text isn't breathing so well inside the bubble because it's so close to the edges.
I hope this helps!
